*inbox*: if empty, only bypass *folder* to $MAIL or builtin default

[s-mailx.git] / nail.1

.\" Copyright (c) 1980, 1990, 1993
.\"     The Regents of the University of California.  All rights reserved.
.\" Copyright (c) 2000
.\"     Gunnar Ritter.  All rights reserved.
.\" Copyright (c) 2012 - 2015 Steffen (Daode) Nurpmeso <sdaoden@users.sf.net>.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"     This product includes software developed by the University of
.\"     California, Berkeley and its contributors.
.\"     This product includes software developed by Gunnar Ritter
.\"     and his contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS 'AS IS' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"--MKREL-START--
.\"@ S-nail(1): v14.8.12 / 2016-10-05
.Dd Oct 05, 2016
.ds VV \\%v14.8.12
.\"--MKREL-END--
.\"--MKMAN-START--
.ds UU \\%S-NAIL
.ds UA \\%S-nail
.ds ua \\%s-nail
.ds UR \\%s-nail.rc
.\"--MKMAN-END--
.\" --BEGINSTRIP--
.\"
.\" If not ~/.mailrc, it breaks POSIX compatibility.  And adjust main.c.
.ds ur \\%~/.mailrc
.ds OB [Obsolete]
.ds OP [Option]
.ds IN [v15-compat]
.ds OU [no v15-compat]
.ds ID [v15 behaviour may differ]
.ds BY (Binary)
.ds RO (Read-only)
.
.Dt "\*(UU" 1
.Os
.Mx -enable
.
.
.Sh NAME
.Nm \*(UA \%[\*(VV]
.Nd send and receive Internet mail
.
.
.\" .Sh SYNOPSIS {{{
.Sh SYNOPSIS
.
.Nm \*(ua
.Fl h | Fl Fl help
.Nm \*(ua
.Bk -words
.Op Fl BDdEFintv~
.Op Fl A Ar account
.Op Fl a Ar attachment
.Op Fl b Ar bcc-addr
.Op Fl c Ar cc-addr
.Op Fl q Ar quote-file
.Op Fl r Ar from-addr
.Op Fl S Ar variable Ns Op Ns = Ns Ar value
.Op Fl s Ar subject
.Op Fl X Ar cmd
.Op Fl \&.
.Ar to-addr ...
.Op Fl Fl \: Ar mta-option ...
.Ek
.Nm \*(ua
.Bk -words
.Op Fl BDdEeHiNnRv~#
.Op Fl A Ar account
.Op Fl L Ar spec-list
.Op Fl r Ar from-addr
.Op Fl S Ar variable Ns Op Ns = Ns Ar value
.Op Fl X Ar cmd
.Fl f Op Ar file
.Op Fl Fl \: Ar mta-option ...
.Ek
.Nm \*(ua
.Bk -words
.Op Fl BDdEeHiNnRv~#
.Op Fl A Ar account
.Op Fl L Ar spec-list
.Op Fl r Ar from-addr
.Op Fl S Ar variable Ns Op Ns = Ns Ar value
.Op Fl u Ar user
.Op Fl X Ar cmd
.Op Fl Fl \: Ar mta-option ...
.Ek
.\" }}}
.
.
.Mx -toc -tree html pdf ps xhtml
.
.
.\" .Sh DESCRIPTION {{{
.Sh DESCRIPTION
.
.Bd -filled -compact -offset indent
.Sy Compatibility note:
S-nail (\*(UA) will wrap up into \%S-mailx in v15.0 (circa 2018).
A partial set of compatibility options exist, tagged as \*(IN and \*(OU.
To choose upward compatible behaviour, please set the internal variable
.Va v15-compat .
Anything which will vanish in v15.0 is tagged \*(OB, and using
.Fl d
will print warnings for many use cases of obsolete features.
.Ed
.
.Pp
\*(UA is a mail processing system with a command syntax reminiscent of
.Xr ed 1
with lines replaced by messages.
It is intended to provide the functionality of the POSIX
.Xr mailx 1
command and offers (mostly optional) extensions for line editing, IDNA,
MIME, S/MIME, SMTP and POP3 (and IMAP).
It is usable as a mail batch language.
.
.\" .Ss "Options" {{{
.Ss "Options"
.
.Bl -tag -width ".Fl _ Ar _ccount"
.Mx
.It Fl A Ar account
Executes an
.Ic account
command (see below) for
.Ar account
after the startup files have been read.
.
.Mx
.It Fl a Ar file
Attach the given file to the message.
The same filename conventions as described in the section
.Sx COMMANDS
apply: shell word expansion is restricted to the tilde
.Ql ~
and variables.
Shall
.Ar file
not be accessible but contain a
.Ql =
character, then anything after the
.Ql =
is assumed to specify the input character set and anything before
.Ql =
the filename: this is the only option to specify the input character set
(and don't perform any character set conversion) for text attachments
from the command line, not using the
.Ic ~@
tilde escape command.
.
.Mx
.It Fl B
Make standard input and standard output line-buffered.
.
.Mx
.It Fl b Ar address
Send blind carbon copies to the given list of addresses.
.Sx Sending mail
below goes into more detail on that.
.
.Mx
.It Fl c Ar address
Send carbon copies to the given list of addresses.
.
.Mx
.It Fl D
\*(OP Set the
.Va disconnected
variable.
.
.Mx
.It Fl d
Set the
.Va debug
variable, which enables debug messages and disables message delivery.
.
.Mx
.It Fl E
Set the
.Va skipemptybody
variable and thus discard messages with an empty message part body.
This is useful for sending messages from scripts.
.
.Mx
.It Fl e
Just check if mail is present in the system mailbox.
If yes, return an exit status of zero, a non-zero value otherwise.
.
.Mx
.It Fl F
Save the message to send in a file named after the local part of the
first recipient's address (instead of in
.Va record Ns ).
.
.Mx
.It Fl f Op Ar file
Read in the contents of the user's
.Ev MBOX
(or the specified file) for processing;
when \*(UA is quit, it writes undeleted messages back to this file
(but be aware of the
.Va hold
option).
Some special conventions are recognized for the string
.Ar file
which are documented for the
.Ic file
command below.
Note that
.Ar file
is not a direct argument to the flag
.Fl f ,
but is instead taken from the command line after option processing has
been completed.
In order to use a
.Ar file
that starts with a hyphen, prefix it with a (relative) path, as in
.Ql ./-hyphenbox.mbox .
.
.Mx
.It Fl H
Print a header summary of all messages and exit.
A configurable summary view is available via the
.Fl L
option.
.
.Mx
.It Fl h
Print a short usage summary.
Because of widespread use a
.Fl Fl help
argument will have the same effect.
.
.Mx
.It Fl i
Set the
.Va ignore
variable to ignore tty interrupt signals.
.
.Mx
.It Fl L Ar spec-list
Print a header summary of only those messages that match the given
.Ar spec-list ,
then exit.
See the section
.Sx "Specifying messages"
for the format of
.Ar spec-list .
If the
.Fl H
option has been given in addition no header summary is produced,
but \*(UA will instead indicate via its exit status whether
.Ar spec-list
matched any messages
.Pf ( Ql 0 )
or not
.Pf ( Ql 1 ) ;
note that any verbose output is suppressed in this mode and must instead
be enabled explicitly (e.g., by using the option
.Fl v ) .
.
.Mx
.It Fl N
Unset the
.Va header
variable and thus inhibit initial display of message headers when
reading mail or editing a mail folder.
.
.Mx
.It Fl n
Inhibits reading
.Pa \*(UR
upon startup.
This option should be activated for \*(UA scripts that are invoked on
more than one machine, because the contents of that file may differ
between them.
(The same behaviour can be achieved by setting the
.Ev NAIL_NO_SYSTEM_RC
environment variable.)
.
.Mx
.It Fl q Ar file
Start the message with the contents of the specified file.
May be given in send mode only.
.
.Mx
.It Fl R
Any folder opened will be in read-only mode.
.
.Mx
.It Fl r Ar address
If
.Ar address
is a valid address then it specifies the envelope sender address to be
passed to the MTA as
.Ql -f Ar address
when a message is send.
Shall
.Ar address
include a user name, comments etc., then the components will be
separated and the name part will be passed to the MTA individually via
.Ql -F Ar name .
The given
.Ar address
will also be assigned to the
.Va from
variable, just as if additionally
.Ql -Sfrom=address
had been specified (therefore affecting SMTP data transfer, too).
.Pp
If instead an empty string is passed as
.Ar address
then the content of the variable
.Va from
will be evaluated and used for this purpose whenever the MTA is
contacted.
Note that \*(UA by default, without
.Fl \&\&r
that is, neither passes
.Ql -f
nor
.Ql -F
flags to the MTA by itself.
.
.Mx
.It Fl S Ar variable Ns Op = Ns value
Sets the internal option
.Ar variable
and, in case of a value option, assigns
.Ar value
to it.
Even though options set via
.Fl S
may be overwritten from within resource files,
the command line setting will be reestablished after all resource files
have been loaded.
.
.Mx
.It Fl s Ar subject
Specify the subject of the to-be-sent message.
.
.Mx
.It Fl t
The message to be sent is expected to contain a message header with
.Ql To: ,
.Ql Cc: ,
or
.Ql Bcc:
fields giving its recipients, which will be added to those given on the
command line.
If a message subject is specified via
.Ql Subject:
then it'll be used in favour of one given on the command line.
.Pp
Also understood are
.Ql Reply-To:
(possibly overriding
.Va replyto ) ,
.Ql Sender:
(p.\ o.\&
.Va sender ) ,
.Ql Organization:
(p.\ o.\&
.Va ORGANIZATION ) .
Note you can also specify
.Ql From: ,
possibly overriding
.Va from
and the envelope address possibly specified with the option
.Fl r !
.Pp
The following, which are normally created automatically based
upon the message context, can also be specified:
.Ql Message-ID: ,
.Ql In-Reply-To: ,
.Ql References:
and
.Ql Mail-Followup-To:
(special address massage will however still occur for the latter).
.
.Mx
.It Fl u Ar user
Read the system mailbox of
.Ar user
(appropriate privileges presumed), and
.Dq assume to be
.Ar user
in some aspects, e.g. in respect to
.Ic file Ns
\(enexpansions of
.Ql %
etc.; also see
.Ev USER .
.
.Mx
.It Fl V
Print \*(UA's version and exit.
.
.Mx
.It Fl v
Setting the
.Va verbose
option causes some verbosity (like printing of certificate chains).
Using it twice increases the level of verbosity.
.
.Mx
.It Fl X Ar cmd
Add the given
.Ar cmd
to the list of commands to be executed before normal operation starts.
Correlates with
.Fl #
and
.Va batch-exit-on-error ;
the only possibility to execute commands in non-interactive mode when
reading startup files is actively prohibited.
.
.Mx
.It Fl ~
Enable
.Sx TILDE ESCAPES
even if not in interactive mode.
.
.Mx
.It Fl #
This sets several options to prepare \*(UA for working in (most likely
non-interactive) batch mode:
.Va dot ,
.Va emptystart ,
.Pf no Va header ,
.Va quiet ,
.Va sendwait ,
as well as
.Ev MBOX
and
.Va folder
(both to
.Pa /dev/null ) .
It also enables processing of
.Sx "TILDE ESCAPES" .
E.g., the following should send an email message to
.Dq bob :
.Bd -literal -offset indent
$ LC_ALL=C printf 'm bob\en~s ubject\enText\en.\enx\en' | \e
  LC_ALL=C MAILRC=/dev/null s-nail -n -# -Snosave
.Ed
.
.Mx
.It Fl \&.
This flag forces termination of option processing in order to prevent
.Dq option injection
(attacks).
It also forcefully puts \*(UA into send mode, see
.Sx "Sending mail" .
.El
.
.Pp
In the above list of supported command line options,
.Fl D , d , E , i , N
and
.Fl v
are implemented by means of setting the respective option, as via
.Fl S .
.Bk -words
.Op Ar mta-option ...
.Ek
arguments that are given at the end of the command line after a
.Ql --
separator will be passed through to the mail-transfer-agent (MTA) and
persist for an entire (interactive) session \(en if the setting of
.Va expandargv
allows their recognition;
MTA arguments can also be specified in the variable
.Va sendmail-arguments ;
find MTA interaction described in more detail in the documentation of
.Va sendmail .
MTA arguments are ignored when mail is send via SMTP data transfer.
.\" }}}
.
.\" .Ss "A starter" {{{
.Ss "A starter"
.
\*(UA is a direct descendant of the BSD Mail program that was introduced
in 1978 (itself superceeding the simpler UNIX mail program) and used
to introduce itself (in the Mail reference manual) as follows:
.
.Bd -ragged -offset indent
Mail provides a simple and friendly environment for sending and
receiving mail.
It divides incoming mail into its constituent messages and allows the
user to deal with them in any order.
In addition, it provides a set of
.Xr ed 1 Ns
-like commands for manipulating messages and sending mail.
Mail offers the user simple editing capabilities to ease the composition
of outgoing messages, as well as providing the ability to define and
send to names which address groups of users.
.Ed
.
.Pp
\*(UA is thus the user side of the Unix mail system, whereas the system
side (mail-transfer-agent, MTA) was traditionally taken by
.Xr sendmail 8 ;
today
.Xr postfix 1
or
.Xr exim 8
are often used for this purpose instead.
If the \*(OPal SMTP feature has been built into \*(UA then the
system side is not a mandatory precondition for mail delivery.
.
.Pp
Because \*(UA strives for compliance with POSIX
.Xr mailx 1
it is likely that some configuration settings have to be adjusted before
using it is a smooth experience.
The default global
.Pa \*(UR
file already bends those standard settings a bit towards more user
friendliness and safety, e.g., it sets the
.Va hold
and
.Va keepsave
options in order to suppress the automatic moving of messages to
.Ev MBOX
that would otherwise occur (see
.Sx "Message states" )
and
.Va keep
to not remove empty files in order not to mangle file permissions when
files eventually get recreated.
It does not set the
.Va folder
option so that by default file grouping (via the
.Ql +
prefix as documented also for
.Ic file )
is not enabled.
The section
.Sx EXAMPLES
contains some further suggestions.
.\" }}}
.
.\" .Ss "Sending mail" {{{
.Ss "Sending mail"
.
To send a message to one or more people, using a local
mail-transfer-agent (MTA; the executable path can be set via
.Va sendmail )
or the \*(OPal builtin SMTP (set and see the variable
.Va smtp )
transport to actually deliver the generated mail message, \*(UA can be
invoked with arguments which are the names of people to whom the mail
will be sent:
.
.Bd -literal -offset indent
$ \*(ua -s Subject -a attachm.ent bill@host1 'Bob <bob@host2>'
# But... try it in an isolated dry-run mode first
$ LC_ALL=C MAILRC=/dev/null \e
  \*(ua -n -d -vv -Sfrom="me <he@re>" \e
    -s Subject -. "(Lovely) Bob <bob@host2>"
.Ed
.
.Pp
The user is then expected to type in the message contents.
In this compose mode \*(UA treats lines beginning with the character
.Ql ~
special \(en these are so-called
.Sx "TILDE ESCAPES"
which can be used to read in files, process shell commands, add and edit
attachments and more; e.g., the tilde escape
.Ql Ic ~e
will start the text editor to revise the message in it's current state,
.Ql Ic ~h
allows editing of the message recipients and
.Ql Ic ~?
gives an overview of available tilde escapes.
Typing control-D
.Ql ^D
at the beginning of an empty line leaves compose mode and causes the
message to be send, whereas typing control-C
.Ql ^C
twice will abort the current letter (saving its contents in the file
denoted by
.Ev DEAD
unless
.Pf no Va save
is set.)
.
.Pp
A number of options can be used to alter default behavior; e.g.,
.Ic set Ns
ting (also via
.Fl S )
.Va editalong
will automatically startup a text editor when compose mode is entered,
.Va askcc
will cause the user to be prompted actively for carbon-copy recipients
and the
.Va dot
option will allow leaving compose mode by writing a line consisting
solely of a dot
.Pf ( Ql \&. ) .
.
.Pp
Very important, though, is to define which
.Sx "Character sets"
may be used when sending messages, usually by setting the option
.Va sendcharsets
accordingly,
having read the section
.Sx "The mime.types files"
to understand how the MIME-type of outgoing attachments is classified
and the knowledge that messages are sent asynchronously unless
.Va sendwait
is set: only with it MTA delivery errors will be recognizable.
.
.Pp
Setting
.Va from
is often necessary (e.g., in conjunction with
.Va smtp )
or desirable, you may want to do some dry-run tests before you go.
Saving a copy of the sent messages in a
.Va record
may also be desirable \(en as for most mailbox file targets some
special conventions are recognized, see the
.Ic file
command for more on that.
The section
.Sx "On URL syntax and credential lookup"
will spread some light on the
.Ql USER@HOST
variable chains as well as on using URLs for accessing protocol-specific
resources, like
.Va smtp ,
and
.Sx EXAMPLES
contains an example configuration for sending messages via some of the
well-known public mail providers;
note it also gives a compact overview on how to setup a secure SSL/TLS
environment.
.
.Pp
Message recipients (as specified on the command line or defined in
.Ql To: ,
.Ql Cc:
or
.Ql Bcc: )
may not only be email addressees but can also be names of mailboxes and
even complete shell command pipe specifications.
Proper quoting may be necessary, e.g., to embed whitespace characters.
(Recall that \*(UA deals with mail standards, therefore those define the
rules with which content is interpreted.)
If the variable
.Va expandaddr
is not set then only network addresses (see
.Xr mailaddr 7
for a description of mail addresses) and plain user names (including MTA
aliases) may be used, other types will be filtered out, giving a warning
message.
.
.\" When changing any of the following adjust any RECIPIENTADDRSPEC;
.\" grep the latter for the complete picture
.Pp
If the variable
.Va expandaddr
is set then extended recipient addresses will optionally be accepted:
Any name which starts with a vertical bar
.Ql |
character specifies a command pipe \(en the command string following the
.Ql |
is executed and the message is sent to its standard input;
Likewise, any name that starts with the character slash
.Ql /
or the character sequence dot slash
.Ql ./
is treated as a file, regardless of the remaining content.
Any other name which contains an at sign
.Ql @
character is treated as a network address;
Any other name which starts with a plus sign
.Ql +
character specifies a mailbox name;
Any other name which contains a slash
.Ql /
character but no exclamation mark
.Ql \&!
or percent sign
.Ql %
character before also specifies a mailbox name;
What remains is treated as a network address.
.
.Bd -literal -offset indent
$ echo bla | \*(ua -Sexpandaddr -s test ./mbox.mbox
$ echo bla | \*(ua -Sexpandaddr -s test '|cat >> ./mbox.mbox'
$ echo safe | LC_ALL=C MAILRC=/dev/null \e
    \*(ua -n -Sv15-compat -Ssendwait -Snosave \e
      -Sexpandaddr=fail,-all,+addr -s test \e
      -. bob@home.net
.Ed
.
.Pp
It is possible to create personal distribution lists via the
.Ic alias
command, so that, for instance, the user can send mail to
.Ql cohorts
and have it go to a group of people:
.
.Pp
.Dl alias cohorts bill jkf mark kridle@ucbcory ~/mail/cohorts.mbox
.
.Pp
Please note that this mechanism has nothing in common with the system
wide aliases that may be used by the local MTA (mail-transfer-agent),
which are subject to the
.Ql name
constraint of
.Va expandaddr
and are often tracked in a file
.Pa /etc/aliases
(and documented in
.Xr aliases 5
and
.Xr sendmail 1 ) .
Personal aliases will be expanded by \*(UA before the message is sent,
and are thus a convenient alternative to specifying each addressee by
itself.
.
.Pp
To avoid environmental noise scripts should
.Dq detach
\*(ua from any configuration files and create a script-local
environment, either by pointing the
.Ev MAILRC
variable to a custom configuration file, or by using the
.Fl S
command line option to specify options:
.
.Bd -literal -offset indent
$ env LC_ALL=C MAILRC=/dev/null password=NOTSECRET \e
  \*(ua -n -Sv15-compat -Ssendwait -Snosave \e
    -Sexpandaddr=fail,-all,+addr \e
    -S 'smtp=smtps://mylogin@some.host:465' -Ssmtp-auth=login \e
    -S 'from=scriptreply@domain' \e
    -s 'subject' -a attachment_file \e
    -. "Recipient 1 <recipient1@domain>" recipient2@domain \e
    < content_file
.Ed
.\" }}}
.
.\" .Ss "Reading mail" {{{
.Ss "Reading mail"
.
When invoked without addressees \*(UA enters interactive mode in which
mails may be read.
When used like that the user's system mailbox
(see the command
.Ic file
for an in-depth description of the different mailbox types that exist)
is read in and a one line header of each message therein is displayed.
The visual style of this summary of
.Ic headers
can be adjusted through the variable
.Va headline
and the possible sorting criterion via
.Va autosort .
Scrolling through
.Va screen Ns
fuls of
.Ic headers
can be performed with the command
.Ic z .
If the initially opened mailbox is empty \*(UA will instead exit
immediately (after displaying a message) unless the variable
.Va emptystart
is found to be set.
.
.Pp
At the
.Va prompt
the command
.Ic list
will give a listing of all available commands and
.Ic help
will give a summary of some common ones.
If the \*(OPal documentation strings are available one can type
.Ql ?X
and see the actual expansion of
.Ql X
and what it's purpose is, i.e., commands can be abbreviated
(note that POSIX defines some abbreviations, so that the alphabetical
order of commands doesn't necessarily relate to the abbreviations; it is
possible to define overwrites with the
.Ic ghost
command, however).
.
.Pp
Messages are given numbers (starting at 1) which uniquely identify
messages; the current message \(en the
.Dq dot
\(en will either be the first new message, or the first unread message,
or the first message of the mailbox; the option
.Va showlast
will instead cause usage of the last message for this purpose.
.
.Pp
Messages can be printed with the
.Ic print
command, or short:
.Ql p .
By default the current message
.Pf ( Dq dot )
is printed, but like with most other commands it is possible to give
a fancy message specification (see
.Sx "Specifying messages" ) ,
e.g.,
.Ql p:u
will display all unread messages,
.Ql p.
will print the
.Dq dot ,
.Ql p 1 5
will print the messages 1 and 5,
.Ql p 1-5
will print the messages 1 through 5, and
.Ql p-
and
.Ql p+
will print the last and the next message, respectively.
.
.Pp
In the default setup all header fields of a message will be printed,
but this can be changed: either by blacklisting a list of fields via
.Ic ignore ,
or by whitelisting only a given list with the
.Ic retain
command, e.g.,
.Ql Ic \:retain Ns \0date from to cc subject .
In order to print all header fields of a message regardless of currently
active ignore or retain lists, use the command
.Ic Print .
The variable
.Va crt
controls whether and when \*(UA will use the configured
.Ev PAGER
for printing instead of directly writing to the terminal (generally
speaking).
.
.Pp
Dependent upon the configuration a
.Sx "Command line editor"
aims at making user experience with the many
.Sx COMMANDS
a bit nicer.
When reading the system mailbox or when
.Fl f
(or
.Ic file )
specified a mailbox explicitly prefixed with the special
.Ql %:
modifier then messages which have been read will be moved to the user's
.Ev MBOX
file automatically when the mailbox is left, either by changing the
active mailbox or by quitting \*(UA (also see
.Sx "Message states" ) .
.
.Pp
After examining a message the user can also
.Ic delete Ql d
the message,
.Ic reply Ql r
to the sender and all recipients or
.Ic Reply Ql R
exclusively to the sender.
Messages can also be
.Ic forward Ns
ed (shorter alias is
.Ic fwd Ns ).
Note that when replying to or forwarding a message recipient addresses
will be stripped from comments and names unless the option
.Va fullnames
is set.
Deletion causes \*(UA to forget about the message;
This is not irreversible, though, one can
.Ic undelete Ql u
the message by giving its number,
or the \*(UA session can be ended by giving the
.Ic exit Ql x
command.
.
.Pp
To end a mail processing session one may either issue
.Ic quit Ql q
to cause a full program exit, which possibly includes
automatic moving of read messages to
.Ev MBOX
as well as updating the \*(OPal command line editor history file,
or use the command
.Ic exit Ql x
instead in order to prevent any of these actions.
.\" }}}
.
.\" .Ss "Viewing HTML mail and MIME attachments" {{{
.Ss "Viewing HTML mail and MIME attachments"
.
Messages which are HTML-only get more and more common and of course many
messages come bundled with a bouquet of MIME attachments.
Whereas \*(UA \*(OPally supports a simple HTML-to-text converter to deal
with HTML messages (see
.Sx "The mime.types files" ) ,
it normally can't deal with any of these itself, but instead programs
need to become registered to deal with specific MIME types or file
extensions.
These programs may either prepare plain text versions of their input
in order to enable \*(UA to display the content on the terminal,
or display the content themselves, for example in a graphical window.
The latter type of programs by default
.Dq blocks
\*(UA until the external viewer has terminated, but asynchronous
side-by-side execution is also possible, in which case \*(UA will
continue to display the message and remain responsive.
.
.Pp
To install an external handler program for a specific MIME type set an
according
.Va pipe-TYPE/SUBTYPE
variable.
To define a handler for a specific file extension set the respective
.Va pipe-EXTENSION
variable \(en these handlers take precedence.
The variable
.Va mime-counter-evidence
can be set to improve dealing with faulty MIME part declarations as are
often seen in real-life messages.
E.g., to display a HTML message inline (that is, converted to a more
fancy plain text representation than the builtin converter is capable to
produce) with either of the text-mode browsers
.Xr lynx 1
or
.Xr elinks 1 ,
teach \*(UA about MathML documents and make it display them as plain text
and to open PDF attachments in an external PDF viewer, asynchronously:
.
.Bd -literal -offset indent
if $features !@ HTML-FILTER
  #set pipe-text/html="elinks -force-html -dump 1"
  set pipe-text/html="lynx -stdin -dump -force_html"
  # Display HTML as plain text instead
  #set pipe-text/html=@
endif
mimetype '@ application/mathml+xml mathml'
set pipe-application/pdf="@&set -C;\e
    : > \e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e"; \e
    trap \e"rm -f \e\e\e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e\e\e"\e" \e
      EXIT INT QUIT PIPE TERM;\e
    set +C;\e
    cat > \e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e"; \e
    xpdf \e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e""
.Ed
.
.Pp
Note: special care must be taken when using such commands as mail
viruses may be distributed by this method: if messages of type
.Ql application/x-sh
or files with the extension
.Ql .sh
were blindly filtered through the shell, for example, a message sender
could easily execute arbitrary code on the system \*(UA is running on.
For more on MIME, also in respect to sending of messages, see the
section
.Sx "The mime.types files"
and the command
.Ic mimetype .
.\" }}}
.
.\" .Ss "Mailing lists" {{{
.Ss "Mailing lists"
.
\*(UA offers some support to ease handling of mailing lists.
The command
.Ic mlist
promotes all given arguments to known mailing lists, and
.Ic mlsubscribe
sets their subscription attribute, creating them first as necessary.
(On the other hand
.Ic unmlsubscribe
doesn't
.Ic unmlist
automatically, but only resets the subscription attribute.)
Using the commands without arguments will print out (a subset of) all
currently defined mailing lists.
The
.Va headline
format
.Ql \&%T
can be used to mark out messages with configured list addresses
in the header display.
.
.Pp
\*(OPally mailing lists may also be specified as regular expressions,
which allows matching of many addresses with a single expression.
However, all fully qualified list addresses are matched via a fast
dictionary, whereas expressions are placed in (a) list(s) which is
(are) matched sequentially.
.
.Bd -literal -offset indent
set followup-to followup-to-honour=ask-yes reply-to-honour=ask-yes
mlist a1@b1.c1 a2@b2.c2 .*@lists.c3$
mlsubscribe a4@b4.c4 exact@lists.c3
.Ed
.
.Pp
The variable
.Va followup-to-honour
will ensure that a
.Ql Mail-\:Followup-\:To:
header is honoured when the message is being replied to (via
.Ic reply
and
.Ic Lreply )
and
.Va followup-to
controls whether this header is created when sending mails; it will be
created automatically for a couple of reasons, too, like when the
special
.Dq mailing list specific
respond command
.Ic Lreply
is used, when
.Ic reply
is used to respond to a message with its
.Ql Mail-Followup-To:
being honoured etc.
.
.Pp
A difference in between the handling of known and subscribed lists is
that the address of the sender is usually not part of a generated
.Ql Mail-Followup-To:
when addressing the latter, whereas it is for the former kind of lists.
Usually because there are exceptions: say, if multiple lists are
addressed and not all of them are subscribed lists.
.Pp
For convenience \*(UA will, temporarily, automatically add a list
address that is presented in the
.Ql List-To:
header of a message that is being responded to to the list of known
mailing lists.
Shall that header have existed \*(UA will instead, dependend on the
variable
.Va reply-to-honour ,
use an also set
.Ql Reply-To:
for this purpose in order to accept a list administrators' wish that
is supposed to have been manifested like that (but only if it provides
a single address which resides on the same domain as what is stated in
.Ql List-To: ) .
.\" }}}
.
.\" .Ss "Resource files" {{{
.Ss "Resource files"
.
Upon startup \*(UA reads in several resource files:
.
.Bl -tag -width ".It Pa _AIL_EXTRA_R_"
.Mx
.It Pa \*(UR
System wide initialization file.
Reading of this file can be suppressed, either by using the
.Fl n
command line option, or by setting the environment variable
.Ev NAIL_NO_SYSTEM_RC .
.
.Mx
.It Pa \*(ur
File giving initial commands.
A different file can be chosen by setting the environment variable
.Ev MAILRC .
.
.It Va NAIL_EXTRA_RC
Can be used to define an optional startup file to be read after
.Pa \*(ur .
This variable is only honoured in certain circumstances (see its
documentation for more).
.El
.
.Pp
The content of these files is interpreted as follows:
.
.Pp
.Bl -bullet -compact
.It
A lines' leading whitespace is ignored.
.It
An empty line is ignored.
.It
If the line (content) starts with the number sign
.Ql #
then it is a comment-command \(en a real command! \(en and also ignored.
This command is the only form of comment that is understood.
.It
A line can be
.Dq continued
on the next line if the newline character is
.Dq escaped
by preceding it with the backslash character
.Ql \e .
Note that any leading whitespace of follow lines is removed:
If whitespace is desired it must be placed before the backslash.
For example:
.
.Bd -literal -offset indent
 # This line is a comment command.  And y\e
    es, it is really continued here.
set debug \e
    verbose
.Ed
.El
.\" }}}
.
.\" .Ss "Character sets" {{{
.Ss "Character sets"
.
\*(OP \*(UA detects the character set of the terminal by using
mechanisms that are controlled by the
.Ev LC_CTYPE
locale setting
(the manual for
.Xr setlocale 3
should give an overview); the \*(UA internal variable
.Va ttycharset
will be set to the detected terminal character set accordingly
and will thus show up in the output of the commands
.Ic set
and
.Ic varshow .
.
.Pp
However, a user supplied
.Va ttycharset
value is not overwritten by this detection mechanism: this
.Dq feature
must be used if the detection doesn't work properly,
and it may be used to adjust the name of the locale character set.
E.g., on BSD systems one may use a locale with the character set
ISO8859-1, which is not a valid name for this character set; to be on
the safe side, one may set
.Va ttycharset
to the correct name, which is ISO-8859-1.
.
.Pp
Note that changing the value doesn't mean much beside that,
since several aspects of the real character set are implied by the
locale environment of the system,
and that stays unaffected by the content of an overwritten
.Va ttycharset
variable.
(This is mostly an issue when interactively using \*(UA, though.
It is actually possible to send mail in a completely
.Dq faked
locale environment.)
.
.Pp
If no character set conversion capabilities have been compiled into
\*(UA (i.e., no
.Xr iconv 3
library has been found), then
.Va ttycharset
will be the only supported character set,
it is simply assumed that it can be used to exchange 8-bit messages,
and the rest of this section does not apply;
it may however still be necessary to explicitly set it if automatic
detection fails, since in that case it defaults to the mentioned
ISO-8859-1.
.
.Pp
When reading messages, their text is converted into
.Va ttycharset
as necessary in order to display them on the users terminal.
Unprintable characters and invalid byte sequences are detected
and replaced by proper substitution characters (unless the variable
.Va print-all-chars
was set once \*(UA was started).
Also see
.Va charset-unknown-8bit
to deal with another hairy aspect of message interpretation.
.
.Pp
When sending messages all their parts and attachments are classified.
Whereas no character set conversion is performed on those parts which
appear to be binary data,
the character set being used must be declared within the MIME header of
an outgoing text part if it contains characters that do not conform to
the set of characters that are allowed by the email standards.
Permissible values for character sets can be declared using the
.Va sendcharsets
variable, and
.Va charset-8bit ,
which defines a catch-all last-resort fallback character set that is
implicitly appended to the list of character-sets in
.Va sendcharsets .
.
.Pp
When replying to a message and the variable
.Va reply-in-same-charset
is set then the character set of the message being replied to is tried
first.
And it is also possible to make \*(UA work even more closely related to
the current locale setting automatically by using the variable
.Va sendcharsets-else-ttycharset ,
please see there for more information.
.
.Pp
All the specified character sets are tried in order unless the
conversion of the part or attachment succeeds.
If none of the tried (8-bit) character sets is capable to represent the
content of the part or attachment,
then the message will not be sent and its text will be saved to
.Ev DEAD .
In general, if the message
.Dq Cannot convert from a to b
appears, either some characters are not appropriate for the currently
selected (terminal) character set,
or the needed conversion is not supported by the system.
In the first case, it is necessary to set an appropriate
.Ev LC_CTYPE
locale and/or the variable
.Va ttycharset .
.
.Pp
The best results are usually achieved when \*(UA is run in a UTF-8
locale on a UTF-8 capable terminal, in which case the full Unicode
spectrum of characters is available.
In this setup characters from various countries can be displayed,
while it is still possible to use more simple character sets for sending
to retain maximum compatibility with older mail clients.
.\" }}}
.
.\" .Ss "Message states" {{{
.Ss "Message states"
.
\*(UA differentiates in between several different message states;
the current state will be reflected in the header display if
.Va headline
is configured to do so.
In \*(UA message states are inspected when leaving a mailbox and may
cause messages to be automatically moved to the special
.Ev MBOX
mailbox \(en because this may be irritating to users which are used to
.Dq more modern
mail-user-agents, the default global
.Pa \*(UR
sets the
.Va hold
and
.Va keepsave
variables in order to suppress this behaviour.
.
.Bl -tag -width ".It Ql _reserved"
.It Ql new
Message has neither been viewed nor moved to any other state.
Such messages are retained even in the system mailbox.
.
.It Ql unread
Message has neither been viewed nor moved to any other state, but the
message was present already when the mailbox has been opened last:
Such messages are retained even in the system mailbox.
.
.It Ql read
The message has been processed by one of the following commands:
.Ic ~f ,
.Ic ~m ,
.Ic ~F ,
.Ic ~M ,
.Ic copy ,
.Ic mbox ,
.Ic next ,
.Ic pipe  ,
.Ic print ,
.Ic Print ,
.Ic top ,
.Ic type ,
.Ic Type ,
.Ic undelete .
The
.Ic delete ,
.Ic dp ,
and
.Ic dt
commands may also cause the next message to be marked as read, depending
on the value of the
.Va autoprint
variable.
Except when the
.Ic exit
command is used, messages that are in the system mailbox or in mailboxes
which were opened with the special
.Ql %:
prefix and are in
.Ql read
state when the mailbox is left will be saved in
.Ev MBOX
unless the option
.Va hold
it set.
.
.It Ql deleted
The message has been processed by one of the following commands:
.Ic delete ,
.Ic dp ,
.Ic dt .
Only
.Ic undelete
can be used to access such messages.
.
.It Ql preserved
The message has been processed by a
.Ic preserve
command and it will be retained in its current location.
.
.It Ql saved
The message has been processed by one of the following commands:
.Ic save
or
.Ic write .
Unless when the
.Ic exit
command is used, messages that are in the system mailbox or in mailboxes
which were opened with the special
.Ql %:
prefix and are in
.Ql saved
state when the mailbox is left will be deleted; they will be saved in
.Ev MBOX
when the option
.Va keepsave
is set.
.El
.\" }}}
.
.\" .Ss "Specifying messages" {{{
.Ss "Specifying messages"
.
Commands such as
.Ic print
and
.Ic delete
can be given a list of message numbers as arguments to apply to a number
of messages at once.
Thus
.Ql delete 1 2
deletes messages 1 and 2,
whereas
.Ql delete 1-5
will delete the messages 1 through 5.
In sorted or threaded mode (see the
.Ic sort
command),
.Ql delete 1-5
will delete the messages that are located between (and including)
messages 1 through 5 in the sorted/threaded order, as shown in the
header summary.
Multiple colon modifiers can be joined into one, e.g.,
.Ql :du .
The following special message names exist:
.
.Bl -tag -width ".It Ar _n_u"
.It Ar :n
All
.Ql new
messages.
.It Ar :o
All old messages (any not in state
.Ql read
or
.Ql new ) .
.It Ar :u
All
.Ql unread
messages.
.It Ar :d
All
.Ql deleted
messages (for the
.Ic undelete
command).
.It Ar :r
All
.Ql read
messages.
.It Ar :f
All
.Ic flag Ns
ged messages.
.It Ar :a
All answered messages
(cf. the
.Va markanswered
variable).
.It Ar :t
All messages marked as draft.
.It Ar :s
\*(OP All messages classified as spam.
.It Ar :S
\*(OP All messages with unsure spam classification.
.It Ar \&.
The current message, the so-called
.Dq dot .
.It Ar \&;
The message that was previously the current message.
.It Ar \&,
The parent message of the current message,
that is the message with the Message-ID given in the
.Ql In-Reply-To:
field or the last entry of the
.Ql References:
field of the current message.
.It Ar -
The next previous undeleted message,
or the next previous deleted message for the
.Ic undelete
command.
In sorted/threaded mode,
the next previous such message in the sorted/threaded order.
.It Ar +
The next undeleted message,
or the next deleted message for the
.Ic undelete
command.
In sorted/threaded mode,
the next such message in the sorted/threaded order.
.It Ar ^
The first undeleted message,
or the first deleted message for the
.Ic undelete
command.
In sorted/threaded mode,
the first such message in the sorted/threaded order.
.It Ar $
The last message.
In sorted/threaded mode,
the last message in the sorted/threaded order.
.
.It Ar & Ns Ar x
In threaded mode,
selects the message addressed with
.Ar x ,
where
.Ar x
is any other message specification,
and all messages from the thread that begins at it.
Otherwise it is identical to
.Ar x .
If
.Ar x
is omitted,
the thread beginning with the current message is selected.
.
.It Ar *
All messages.
.It Ar `
All messages that were included in the message list for the previous
command.
.
.It Ar / Ns Ar string
All messages that contain
.Ar string
in the subject field (case ignored).
See also the
.Va searchheaders
variable.
If
.Ar string
is empty,
the string from the previous specification of that type is used again.
.
.It Xo Op Ar @ Ns Ar name-list Ns
.Ar @ Ns Ar expr
.Xc
All messages that contain the given case-insensitive search
.Ar expr Ns
ession; if the \*(OPal regular expression (see
.Xr re_format 7 )
support is available
.Ar expr
will be interpreted as one if any of the
.Dq magical
regular expression characters is seen.
If the optional
.Ar @ Ns Ar name-list
part is missing, the search is restricted to the subject field body,
but otherwise
.Ar name-list
specifies a comma-separated list of header fields to search, as in
.Pp
.Dl '@to,from,cc@Someone i ought to know'
.Pp
In order to search for a string that includes a
.Ql @
(commercial at) character the
.Ar name-list
is effectively non-optional, but may be given as the empty string.
Some special header fields may be abbreviated:
.Ql f ,
.Ql t ,
.Ql c ,
.Ql b
and
.Ql s
will match
.Ql From ,
.Ql To ,
.Ql Cc ,
.Ql Bcc
and
.Ql Subject ,
respectively and case-insensitively.
The special names
.Ql header
or
.Ql <
can be used to search in (all of) the header(s) of the message, and the
special names
.Ql body
or
.Ql >
and
.Ql text
or
.Ql =
can be used to perform full text searches \(en whereas the former
searches only the body, the latter also searches the message header.
.Pp
This message specification performs full text comparison, but even with
regular expression support it is almost impossible to write a search
expression that savely matches only a specific address domain.
To request that the content of the header is treated as a list of
addresses, and to strip those down to the plain email address which the
search expression is to be matched against, prefix the header name
(abbreviation) with a tilde
.Ql ~ :
.Pp
.Dl '@~f@@a\e.safe\e.domain\e.match$'
.
.It Ar address
A case-insensitive
.Dq any substring matches
search against the
.Ql From:
header, which will match addresses (too) even if
.Va showname
is set (and POSIX says
.Dq any address as shown in a header summary shall be matchable in this form ) ;
However, if the
.Va allnet
variable is set, only the local part of the address is evaluated
for the comparison, not ignoring case, and the setting of
.Va showname
is completely ignored.
For finer control and match boundaries use the
.Ql @
search expression; the \*(OPal IMAP-style
.Ql (from address)
expression can also be used if substring matches are desired.
.El
.
.Pp
\*(OP IMAP-style SEARCH expressions may also be used.
This addressing mode is available with all types of folders;
\*(UA will perform the search locally as necessary.
Strings must be enclosed by double quotes
.Ql \&"
in their entirety if they contain white space or parentheses;
within the quotes, only backslash
.Ql \e
is recognized as an escape character.
All string searches are case-insensitive.
When the description indicates that the
.Dq envelope
representation of an address field is used,
this means that the search string is checked against both a list
constructed as
.
.Bd -literal -offset indent
(\*qname\*q \*qsource\*q \*qlocal-part\*q \*qdomain-part\*q)
.Ed
.
.Pp
for each address,
and the addresses without real names from the respective header field.
These search expressions can be nested using parentheses, see below for
examples.
.
.Pp
.Bl -tag -compact -width ".It Ar _n_u"
.It Ar ( criterion )
All messages that satisfy the given
.Ar criterion .
.It Ar ( criterion1 criterion2 ... criterionN )
All messages that satisfy all of the given criteria.
.
.It Ar ( or criterion1 criterion2 )
All messages that satisfy either
.Ar criterion1
or
.Ar criterion2 ,
or both.
To connect more than two criteria using
.Ql or
specifications have to be nested using additional parentheses,
as with
.Ql (or a (or b c)) ,
since
.Ql (or a b c)
really means
.Ql ((a or b) and c) .
For a simple
.Ql or
operation of independent criteria on the lowest nesting level,
it is possible to achieve similar effects by using three separate
criteria, as with
.Ql (a) (b) (c) .
.
.It Ar ( not criterion )
All messages that do not satisfy
.Ar criterion .
.It Ar ( bcc \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in the envelope representation of the
.Ql Bcc:
field.
.It Ar ( cc \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in the envelope representation of the
.Ql Cc:
field.
.It Ar ( from \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in the envelope representation of the
.Ql From:
field.
.It Ar ( subject \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in the
.Ql Subject:
field.
.It Ar ( to \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in the envelope representation of the
.Ql To:
field.
.It Ar ( header name \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in the specified
.Ql Name:
field.
.It Ar ( body \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in their body.
.It Ar ( text \*q Ns Ar string Ns Ar \*q )
All messages that contain
.Ar string
in their header or body.
.It Ar ( larger size )
All messages that are larger than
.Ar size
(in bytes).
.It Ar ( smaller size )
All messages that are smaller than
.Ar size
(in bytes).
.
.It Ar ( before date )
All messages that were received before
.Ar date ,
which must be in the form
.Ql d[d]-mon-yyyy ,
where
.Ql d
denotes the day of the month as one or two digits,
.Ql mon
is the name of the month \(en one of
.Ql Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec ,
and
.Ql yyyy
is the year as four digits, e.g.,
.Ql 28-Dec-2012 .
.
.It Ar ( on date )
All messages that were received on the specified date.
.It Ar ( since date )
All messages that were received since the specified date.
.It Ar ( sentbefore date )
All messages that were sent on the specified date.
.It Ar ( senton date )
All messages that were sent on the specified date.
.It Ar ( sentsince date )
All messages that were sent since the specified date.
.It Ar ()
The same criterion as for the previous search.
This specification cannot be used as part of another criterion.
If the previous command line contained more than one independent
criterion then the last of those criteria is used.
.El
.\" }}}
.
.\" .Ss "On URL syntax and credential lookup" {{{
.Ss "On URL syntax and credential lookup"
.
\*(IN For accessing protocol-specific resources, like POP3 mailboxes,
usage of compact and standardized Uniform Resource Locators
(URL, RFC 1738) has become omnipresent.
\*(UA expects and understands URLs in the following form;
parts in brackets
.Ql []
denote optional parts, optional either because there also exist other
ways to define the information in question or because support of the
part is protocol-specific \(en e.g.,
.Ql /path
is used by the IMAP protocol but not by POP3.
.
.Pp
.Dl PROTOCOL://[USER[:PASSWORD]@]server[:port][/path]
.
.Pp
If
.Ql USER
and
.Ql PASSWORD
are specified as part of an URL they must be given in URL percent
encoded (RFC 3986) form \(en the command
.Ic urlencode
can be used to perform the encoding and show the encoded value.
(This doesn't really conform to any standard, but for one it isn't
used for any data exchange over the internet, and second it's easier for
users to simply call
.Ic urlencode
on a string and use that instead of having to deal with several
different standards.)
On the other hand, values given in variables are expected not to be URL
percent encoded.
.
.Pp
Many variable options of \*(UA exist in multiple versions, called
variable chains for the rest of this document: the plain
.Ql variable
as well as
.Ql variable-HOST
and
.Ql variable-USER@HOST .
Here
.Ql HOST
indeed means
.Ql server:port
if a
.Ql port
had been specified in the respective URL, otherwise it refers to the plain
.Ql server .
Also,
.Ql USER
isn't truly the
.Ql USER
that had been found when doing the user chain lookup as is described
below, i.e., this
.Ql USER
will never be in URL percent encoded form, whether it came from an URL or not.
.
.Pp
For example, whether an hypothetical URL
.Ql smtp://hey%3Ayou@our.house
had been given that includes a user, or whether the URL was
.Ql smtp://our.house
and the user had been found differently, to lookup the variable chain
.Va smtp-use-starttls
\*(UA first looks for whether
.Ql smtp-\:use-\:starttls-\:hey:you@our.house
is defined, then whether
.Ql smtp-\:use-\:starttls-\:our.house
exists before finally ending up looking at the plain variable itself.
.
.Pp
\*(UA obeys the following logic scheme when dealing with the
necessary credential informations of an account:
.
.Bl -bullet
.It
If no
.Ql USER
has been given in the URL the variables
.Va user-HOST
and
.Va user
are looked up; if no such variable(s) can be found then \*(UA will,
when enforced by the \*(OPal variables
.Va netrc-lookup-HOST
or
.Va netrc-lookup ,
search the users
.Pa .netrc
file for a
.Ql HOST
specific entry which provides a
.Ql login
name: this lookup will only succeed if unambiguous (one possible matching
entry for
.Ql HOST ) .
.Pp
If there is still no
.Ql USER
then \*(UA will fall back to the user who is supposed to run \*(UA:
either the name that has been given with the
.Fl u
command line option (or, equivalently, but with less precedence, the
environment variable
.Ev USER ) ,
or the
.Dq current
user.
The identity of this user has been fixated during \*(UA startup and is
known to be a valid user on the current host.
.
.It
Authentication: unless otherwise noted this will lookup the
.Va PROTOCOL-auth-USER@HOST , PROTOCOL-auth-HOST , PROTOCOL-auth
variable chain, falling back to a protocol-specific default should this
have no success.
.
.It
If no
.Ql PASSWORD
has been given in the URL \(en it should be noted once that specifying
the password in the URL is only syntactic sugar for the user, it'll
never be part of an URL that \*(UA uses itself \(en, then if the
.Ql USER
has been found through the \*(OPal
.Pa .netrc
file lookup then that may have already provided the password, too.
Otherwise the variable chain
.Va password-USER@HOST , password-HOST , password
is looked up.
.Pp
\*(OP Then if any of the variables of the chain
.Va agent-shell-lookup-USER@HOST , agent-shell-lookup-HOST , \
  agent-shell-lookup
is set the shell command specified therein is run and the output (less
newline characters) will be used as the password.
It is perfectly valid for such an agent to simply not return any data,
in which case the password lookup is continued somewhere else;
Any command failure is treated as a hard error, however.
.Pp
The next variable chain that is inspected is the \*(OPal
.Va netrc-lookup-USER@HOST , netrc-lookup-HOST , netrc-lookup ,
but this time looking only for the password (multiple user accounts
for a single machine may exist as well as a fallback entry without
user but with a password).
.Pp
If at that point there is still no password available, but the
(protocols') chosen authentication type requires a password, then in
interactive mode the user will be prompted on the terminal.
.El
.
.Pp
.Sy Note:
S/MIME verification works relative to the values found in the
.Ql From:
(or
.Ql Sender: )
header field(s), which means that the values of
.Va smime-sign , smime-sign-cert , smime-sign-include-certs
and
.Va smime-sign-message-digest
will not be looked up using the
.Ql USER
and
.Ql HOST
chains from above but instead use the corresponding values from the
message that is being worked on.
In unusual cases multiple and different
.Ql USER
and
.Ql HOST
combinations may therefore be involved \(en on the other hand those
unusual cases become possible.
The usual case is as short as:
.
.Pp
.Dl set smtp=smtp://USER:PASS@HOST smtp-use-starttls \e
.Dl \ \ \ \ smime-sign smime-sign-cert=+smime.pair
.
.Pp
The section
.Sx EXAMPLES
contains complete example configurations.
.\" }}}
.
.\" .Ss "Command line editor" {{{
.Ss "Command line editor"
.
\*(OP \*(UA can be configured to support a command line editor and
command history lists which are saved in between sessions.
One may link against fully-fledged external libraries
.Pf ( Xr readline 6 ,
.Xr editline 3 Ns
) or use \*(UA's own command line editor NCL (Nail-Command-Line)
instead, which should work in all environments which comply to the
ISO C standard (ISO/IEC 9899:1990/Amendment 1:1995).
When an external library is used, interactive behaviour of \*(UA relies
on that library and may not correspond one-to-one to what is described
in this manual.
.
.Pp
Regardless of the actually used command line editor
.Ic history
entries will be created for lines entered in command mode only, and
creation of such an entry can be forcefully suppressed by starting the
line with a space character.
Note that
.Ic history
handling is by itself an optional feature and may therefore not be
available.
For more information see the documentation of the options
.Va emptystart ,
.Va history-gabby ,
.Va history-gabby-persist ,
.Va line-editor-disable ,
.Va NAIL_HISTFILE
and
.Va NAIL_HISTSIZE .
.
.Pp
The builtin \*(UA command line editor supports the following operations;
the notation
.Ql ^-character
stands for the combination of the
.Dq Control
key plus the mentioned character, e.g.,
.Ql ^A
means
.Dq hold down control key and press the A key :
.
.Pp
.Bl -tag -compact -width "Ql _M"
.It Ql ^A
Go to the start of the line.
.It Ql ^B
Move the cursor backward one character.
.It Ql ^D
Forward delete the character under the cursor;
quits \*(UA if used on the empty line unless the
.Va ignoreeof
option is set.
.It Ql ^E
Go to the end of the line.
.It Ql ^F
Move the cursor forward one character.
.
.It Ql ^G
Cancel current operation, full reset.
If there is an active history search or tabulator expansion then this
command will first reset that, reverting to the former line content;
thus a second reset is needed for a full reset in this case.
In all cases \*(UA will reset a possibly used multibyte character input
state machine.
.
.It Ql ^H
The same as
.Dq backspace :
backward delete one character.
.
.It Ql ^I
\*(OP The same as
.Dq horizontal tabulator :
try to expand the word before the cursor.
(Note this is not
.Dq tabulator-completion
as is known from the
.Xr sh 1
but really means the usual \*(UA expansion, as documented for
.Ic file ,
yet it involves shell expansion as a last step, too.)
.
.It Ql ^J
The same as
.Dq ENTER :
complete this line of input.
.It Ql ^K
Delete all characters from the cursor to the end of the line.
.It Ql ^L
Repaint the line.
.It Ql ^N
\*(OP Go to the next history entry.
.It Ql ^O
Execute the command
.Ic dp .
.It Ql ^P
\*(OP Go to the previous history entry.
.It Ql ^R
\*(OP Complete the current line from (the remaining older) history entries.
.It Ql ^U
The same as
.Ql ^A
followed by
.Ql ^K .
.It Ql ^W
Delete the characters from the one preceding the cursor to the preceding
word boundary.
.It Ql ^X
Move the cursor forward one word boundary.
.It Ql ^Y
Move the cursor backward one word boundary.
.El
.
.Pp
If problems with commands that are based upon rightwise movement are
encountered, adjustments of the option
.Va line-editor-cursor-right
may solve the problem, as documented for it.
.
.Pp
If the terminal produces key sequences which are compatible with
.Xr xterm 1
then the left and right cursor keys will map to
.Ql ^B
and
.Ql ^F ,
respectively, the up and down cursor keys will map to
.Ql ^P
and
.Ql ^N ,
and the Home/End/PgUp/PgDown keys will call the
.Ic z
command with the respective arguments
.Ql 0 ,
.Ql $ ,
.Ql -
and
.Ql +
(i.e., perform scrolling through the header summary list).
.\" }}}
.
.\" .Ss "Coloured message display" {{{
.Ss "Coloured message display"
.
\*(OP \*(UA can be configured to support coloured message display,
realized by emitting ANSI colour escape sequences.
Colours are only used when the
.Ev TERM
environment variable is set and either the terminal type can be found in
.Va colour-terms
or its name includes the string
.Ql color .
.
.Pp
On top of that the binary option
.Va colour-pager
defines whether these colour sequences are also generated when the output
of a command needs to go through the
.Ev PAGER
(also see
.Va crt Ns
) \(en this is not enabled by default because different pager programs
need different command line switches or other configuration in order to
support those colour sequences, please see the option for more details.
.
.Pp
To forcefully disable all colour support, set
.Va colour-disable .
.
.Pp
Colours can be configured through font attributes
.Pf ( Ql ft=
\(en
.Ql bold ,
.Ql invers
and
.Ql underline ) ,
foreground
.Pf ( Ql fg= )
and background
.Pf ( Ql bg= )
colours
.Pf ( Ql black ,
.Ql blue ,
.Ql green ,
.Ql red ,
.Ql brown ,
.Ql magenta ,
.Ql cyan
and
.Ql white ) .
Multiple specifications can be joined in a comma separated list, as in
.
.Pp
.Dl set colour-msginfo="ft=bold,fg=magenta,bg=cyan"
.
.Pp
Options to be set are
.Va colour-msginfo ,
.Va colour-partinfo ,
.Va colour-from_ ,
.Va colour-header
and
.Va colour-uheader ,
as well as
.Va colour-user-headers ,
which is a list of headers to be colourized via
.Va colour-uheader
instead of the default
.Va colour-header .
.\" }}}
.\" }}} (DESCRIPTION)
.
.
.\" .Sh COMMANDS {{{
.Sh COMMANDS
.
Each command is typed on a line by itself,
and may take arguments following the command word.
The command need not be typed in its entirety \(en
the first command which matches the typed prefix is used.
(The command
.Ic list
prints a sorted list of available commands, and the command
.Ic help
(or
.Ic \&? ) ,
when given an argument, will show a documentation string for the
expansion, as in
.Ql ?unc ;
documentation strings are however \*(OPal.)
.
.Pp
For commands which take message lists as arguments, the next message
forward that satisfies the command's requirements will be used shall no
explicit message list have been passed.
If there are no messages forward of the current message,
the search proceeds backwards,
and if there are no good messages at all,
\*(UA types
.Dq no applicable messages
and aborts the command.
The arguments to commands can be quoted, using the following methods:
.
.Pp
.Bl -bullet -compact -offset indent
.It
An argument can be enclosed between paired double-quotes
.Ql """argument"""
or
single-quotes
.Ql 'argument' ;
any white space, shell word expansion, or backslash characters (except
as described next) within the quotes are treated literally as part of
the argument.
A double-quote will be treated literally within single-quotes and vice
versa.
Inside such a quoted string the actually used quote character can be
used nonetheless by escaping it with a backslash
.Ql \e ,
as in
.Ql """y\e""ou""" .
.
.It
An argument that is not enclosed in quotes, as above, can usually still
contain space characters if those spaces are backslash-escaped.
.
.It
A backslash outside of the enclosing quotes is discarded
and the following character is treated literally as part of the argument.
.
.It
An unquoted backslash at the end of a command line is discarded and the
next line continues the command.
.El
.
.Pp
Filenames, where expected, are subsequently subjected to the following
transformations, in sequence:
.
.Pp
.Bl -bullet -compact -offset indent
.It
If the filename begins with an unquoted plus sign, and the
.Va folder
variable is defined,
the plus sign will be replaced by the value of the
.Va folder
variable followed by a slash.
If the
.Va folder
variable is unset or is set to null, the filename will be unchanged.
.
.It
Shell word expansions are applied to the filename.
.\" TODO shell word expansion shell expand fexpand FEXP_NSHELL
.Sy Compatibility note:
on the long run support for complete shell word expansion will be
replaced by an internally implemented restricted expansion mechanism in
order to circumvent possible security impacts through shell expansion.
Expect that a growing number of program parts only support this
restricted syntax:
.Pp
Meta expansions are applied to the filename: leading tilde characters
.Pf ( Ql ~/ )
will be replaced by the expansion of
.Ev HOME ,
and any occurrence of
.Ql $VARIABLE
(or
.Ql ${VARIABLE} )
will be replaced by the expansion of the variable, if possible;
\*(UA internal as well as environmental (shell) variables can be
accessed through this mechanism.
In order to include a raw
.Ql $
character precede it with a backslash
.Ql \e ,
to include a backslash double it.
If more than a single pathname results from this expansion and the
command is expecting one file, an error results.
.Pp
Note that in interactive display context, in order to allow simple
value acceptance (typing
.Dq ENTER ) ,
backslash quoting is performed automatically as necessary, e.g., a file
.Ql diet\e is \ecurd.txt
will be displayed as
.Ql diet\e\e is \e\ecurd.txt .
.El
.
.Pp
The following commands are available:
.
.Bl -tag -width ".Ic _ccount"
.Mx
.It Ic #
The comment-command causes the entire line to be ignored.
.Sy Note:
this really is a normal command which' purpose is to discard its
arguments, not a
.Dq comment-start
indicating special character, which means that, e.g., trailing comments
on a line are not possible.
.
.Mx
.It Ic ~
Interprets the remainder of the word as a macro name and passes it
through to the
.Ic call
command; e.g.,
.Ql ~ Ns Ar mymacro
is a shorter synonym for
.Ql call Ar mymacro .
.
.Mx
.It Ic -
Print out the preceding message.
If given a numeric argument n,
goes to the n'th previous message and prints it.
.
.Mx
.It Ic =
Show the current message number (the
.Dq dot ) .
.
.Mx
.It Ic \&?
Prints a brief summary of commands.
\*(OP Given an argument a synopsis for the command in question is
printed instead;
commands can be abbreviated in general and this command can be used
to see the full expansion of an abbreviation including the synopsis,
try, e.g.,
.Ql ?h ,
.Ql ?hel
and
.Ql ?help
and see how the display changes.
.
.Mx
.It Ic \&!
Executes the
.Ev SHELL
(see
.Xr sh 1 Ns
) command which follows.
.
.Mx
.It Ic \&|
A synonym for the
.Ic pipe
command.
.
.Mx
.It Ic account
(ac) Creates, selects or lists (an) account(s).
An account is a group of commands and variable settings which together
usually arrange the environment for the purpose of creating a system login.
Without any argument a listing of all defined accounts and their content
is printed.
A specific account can be activated by giving solely its name, resulting
in the system mailbox or inbox of that account to be activated as via an
explicit use of the command
.Ic file .
The two argument form is identical to defining a macro as via
.Ic define .
For example:
.Bd -literal -offset indent
account myisp {
  set folder=imaps://mylogin@imap.myisp.example
  set record=+Sent
  set from="myname@myisp.example (My Name)"
  set smtp=smtp://mylogin@smtp.myisp.example
}
.Ed
.Pp
creates an account named
.Ql myisp
which can later be selected by specifying
.Ql account myisp .
The special account
.Ql null
(case-insensitive) always exists.
.Ic localopts
can be used to localize account settings \(en different to normal macros
the settings will be reverted once the account is switched off.
Accounts can be deleted via
.Ic unaccount .
.
.Mx
.It Ic alias
(a) With no arguments, prints out all currently-defined aliases.
With one argument, prints out that alias.
With more than one argument,
creates a new alias or appends to an existing one.
.Ic unalias
can be used to delete aliases.
.
.Mx
.It Ic alternates
(alt) Manage a list of alternate addresses / names of the active user,
members of which will be removed from recipient lists when replying to
messages (and the
.Va metoo
variable is not set).
If arguments are given the set of alternate names is replaced by them,
without arguments the current set is displayed.
.
.Mx
.It Ic answered
Takes a message list and marks each message as having been answered.
This mark has no technical meaning in the mail system;
it just causes messages to be marked in the header summary,
and makes them specially addressable.
.
.Mx
.It Ic cache
\*(OP Only applicable to cached IMAP mailboxes;
takes a message list and reads the specified messages into the IMAP
cache.
.
.Mx
.It Ic call
Calls a macro that has been created via
.Ic define .
.
.Mx
.It Ic cd
(ch) Change the working directory to
.Ev HOME
or the given argument.
Synonym for
.Ic chdir .
.
.Mx
.It Ic certsave
\*(OP Only applicable to S/MIME signed messages.
Takes a message list and a file name and saves the certificates
contained within the message signatures to the named file in both
human-readable and PEM format.
The certificates can later be used to send encrypted messages to the
respective message senders by setting
.Va smime-encrypt-USER@HOST
variables.
.
.Mx
.It Ic chdir
(ch) Change the working directory to
.Ev HOME
or the given argument.
Synonym for
.Ic cd .
.
.Mx
.It Ic collapse
Only applicable to threaded mode.
Takes a message list and makes all replies to these messages invisible
in header summaries, unless they are in state
.Ql new .
.
.Mx
.It Ic connect
\*(OP If operating in disconnected mode on an IMAP mailbox,
switch to online mode and connect to the mail server while retaining
the mailbox status.
See the description of the
.Va disconnected
variable for more information.
.
.Mx
.It Ic Copy
(C) Copy messages to files whose names are derived from the author of
the respective message and don't mark them as being saved;
otherwise identical to
.Ic Save .
.
.Mx
.It Ic copy
(c) Copy messages to the named file and don't mark them as being saved;
otherwise identical to
.Ic save .
.
.Mx
.It Ic cwd
Print the current working directory.
.
.Mx
.It Ic Decrypt
\*(OP For unencrypted messages this command is identical to
.Ic Copy ;
Encrypted messages are first decrypted, if possible, and then copied.
.
.Mx
.It Ic decrypt
\*(OP For unencrypted messages this command is identical to
.Ic copy ;
Encrypted messages are first decrypted, if possible, and then copied.
.
.Mx
.It Ic define
Without arguments the current list of macros, including their content,
is printed, but otherwise a macro is defined.
A macro definition is a sequence of commands in the following form:
.Bd -literal -offset indent
define name {
  command1
  command2
  ...
  commandN
}
.Ed
.Pp
A defined macro can be invoked explicitly by using the
.Ic call
or
.Ic ~
commands, or implicitly by setting the
.Va folder-hook
or
.Va folder-hook-FOLDER
variables.
Note that interpretation of
.Ic localopts
depends on how (i.e.,
.Dq as what :
normal macro, folder hook, account switch) the macro is invoked.
Macros can be deleted via
.Ic undefine .
.
.Mx
.It Ic delete
(d) Marks the given message list as
.Ql deleted .
Deleted messages will neither be saved in
.Ev MBOX
nor will they be available for most other commands.
.
.Mx
.It Ic discard
(di) Identical to
.Ic ignore .
Also see
.Ic retain .
.
.Mx
.It Ic disconnect
\*(OP (disco) If operating in online mode on an IMAP mailbox,
switch to disconnected mode while retaining the mailbox status.
See the description of the
.Va disconnected
variable for more.
A list of messages may optionally be given as argument;
the respective messages are then read into the cache before the
connection is closed.
Thus `disco *' makes the entire mailbox available for disconnected use.
.
.Mx
.Mx
.It Ic dp , dt
Deletes the current message and prints the next message.
If there is no next message, \*(UA says
.Dq at EOF .
.
.Mx
.It Ic draft
Takes a message list and marks each given message as a draft.
This mark has no technical meaning in the mail system;
it just causes messages to be marked in the header summary,
and makes them specially addressable.
.
.Mx
.It Ic echo
(ec) Echoes its arguments,
resolving special names as documented for the command
.Ic file .
The escape sequences
.Ql \ea ,
.Ql \eb ,
.Ql \ec ,
.Ql \ef ,
.Ql \en ,
.Ql \er ,
.Ql \et ,
.Ql \ev ,
.Ql \e\e
and
.Ql \e0octal-num
are interpreted just as they are by
.Xr printf 1
(proper quoting provided).
.
.Mx
.It Ic edit
(e) Point the text editor (as defined in
.Ev EDITOR )
at each message from the given list in turn.
Modified contents are discarded unless the
.Va writebackedited
variable is set.
.
.Mx
.It Ic elif
Part of the
.Ic if Ns / Ns Ic elif Ns / Ns Ic else Ns / Ns Ic endif
conditional \(em if the condition of a preceeding
.Ic if
was false, check the following condition and execute the following block
if it evaluates true.
.
.Mx
.It Ic else
(el) Part of the
.Ic if Ns / Ns Ic elif Ns / Ns Ic else Ns / Ns Ic endif
conditional \(em if none of the conditions of the preceeding
.Ic if
and
.Ic elif
commands was true, the
.Ic else
block is executed.
.
.Mx
.It Ic endif
(en) Marks the end of an
.Ic if Ns / Ns Ic elif Ns / Ns Ic else Ns / Ns Ic endif
conditional execution block.
.
.Mx
.It Ic errors
\*(OP Since \*(UA uses the console as a user interface it can happen
that messages scroll by too fast to become recognized.
Optionally an error message ring queue is available which stores
duplicates of any error message and notifies the user in interactive
sessions whenever a new error has occurred.
The queue is finite: if its maximum size is reached any new message
replaces the eldest.
The command
.Ic errors
can be used to manage this message queue: if given
.Ar show
or no argument the queue will be displayed and cleared,
.Ar clear
will only clear all messages from the queue.
.
.Mx
.It Ic exit
(ex or x) Exit from \*(UA without changing the active mailbox and skip
any saving of messages in
.Ev MBOX
as well as a possibly tracked command line editor history file.
.
.Mx
.It Ic features
Print the list of features that have been compiled into \*(UA.
.
.Mx
.It Ic File
(Fi) Like
.Ic file ,
but open the mailbox readonly.
.
.Mx
.It Ic file
(fi) The file command switches to a new mailbox.
Without arguments it prints the complete state of the current mailbox.
If an argument is given, it will write out changes (such as deletions)
the user has made and open a new mailbox.
Some special conventions are recognized for the
.Ar name
argument:
.Pp
.Bl -tag -compact -offset indent -width ".Ar %:__lespec"
.It Ar #
(number sign) means the previous file,
.It Ar %
(percent sign) means the invoking user's system mailbox, which either is
the (itself expandable)
.Va inbox
if that is set (\*(ID and non-empty), the standardized absolute pathname
indicated by
.Ev MAIL
if that is set, or a builtin compile-time default otherwise.
(\*(OB For IMAP folders only, and only if
.Va inbox
is not set, the value of
.Va folder
is inspected and used if found.)
.It Ar %user
means the system mailbox of
.Ar user
(and never the value of
.Va inbox
nor
.Va folder ,
regardless of their actual setting),
.It Ar &
(ampersand) means the invoking user's
.Ev MBOX
file and
.It Ar +file
means a
.Ar file
in the
.Va folder
directory.
.It Ar %:filespec
expands to the same value as
.Ar filespec ,
but the file is handled as a system mailbox by, e.g., the
.Ic mbox
and
.Ic save
commands, meaning that messages that have been read in the current
session will be moved to the
.Ev MBOX
mailbox instead of simply being flagged as read.
.El
.Pp
If the name matches one of the strings defined with the command
.Ic shortcut ,
it is replaced by its long form and expanded.
If the name ends with
.Ql .gz ,
.Ql .bz2
or
.Ql .xz
it is treated as being compressed with
.Xr gzip 1 ,
.Xr bzip2 1
or
.Xr xz 1 ,
respectively, and transparently handled through an intermediate
(un)compression step (using a temporary file) with the according
facility, sufficient support provided.
Likewise, if the named file doesn't exist, but a file with one of the
mentioned compression extensions does, then the name is automatically
expanded and the compressed file is used.
.Pp
Otherwise, if the name ends with an extension for which
.Va file-hook-load-EXTENSION
and
.Va file-hook-save-EXTENSION
variables are set, then the given hooks will be used to load and save
.Dq name ,
and \*(UA will work with an intermediate temporary file.
.Pp
MBOX files (flat file-based mailboxes) are generally locked during file
operations in order to avoid inconsistencies against concurrent
modifications.
Mailbox files which \*(UA treats as system mailboxes will also be
protected by so-called dotlock files, the traditional way of mail spool
file locking: for any file
.Ql a
a lock file
.Ql a.lock
will be created for the duration of the synchronization \(em
as necessary a privilege-separated dotlock child process will be used
to accommodate for necessary privilege adjustments in order to create
the dotlock file in the same directory
and with the same user and group identities as the file of interest.
.Pp
If
.Ar name
refers to a directory with the subdirectories
.Ql tmp ,
.Ql new
and
.Ql cur ,
then it is treated as a folder in
.Dq Maildir
format.
A name of the form
.Pp
.Dl \*(IN protocol://[user[:password]@]host[:port][/path]
.Dl \*(OU protocol://[user@]host[:port][/path]
.Pp
is taken as an Internet mailbox specification.
The \*(OPally supported protocols are
.Ar pop3
(POP3) and
.Ar pop3s
(POP3 with SSL/TLS encrypted transport).
The
.Ar [/path]
part is valid only for IMAP; there it defaults to
.Ar INBOX .
Also see the section
.Sx "On URL syntax and credential lookup" .
.Pp
\*(OU If
.Ar user
contains special characters, in particular
.Ql /
or
.Ql % ,
they must be escaped in URL notation \(en the command
.Ic urlencode
can be used to show the necessary conversion.
The optional `path' part applies to IMAP only;
if it is omitted, the default `INBOX' is used.
.Pp
If \*(UA is connected to an IMAP server,
a name of the form `@mailbox' refers to the `mailbox' on that server,
but otherwise a `@' prefix has no special meaning.
.
.Mx
.It Ic flag
Takes a message list and marks the messages as
.Ic flag Ns
ged for urgent/special attention.
This mark has no technical meaning in the mail system;
it just causes messages to be highlighted in the header summary,
and makes them specially addressable.
.
.Mx
.It Ic folder
(fold) The same as
.Ic file .
.
.Mx
.It Ic folders
With no arguments, list the names of the folders in the folder directory.
With an existing folder as an argument,
lists the names of folders below the named folder;
e.\|g. the command `folders @' lists the folders on the base level of
the current IMAP server.
See also the variable
.Va imap-list-depth .
.
.Mx
.It Ic Followup
(F) Similar to
.Ic Respond ,
but saves the message in a file named after the local part of the first
recipient's address (instead of in
.Va record Ns ).
.
.Mx
.It Ic followup
(fo) Similar to
.Ic respond ,
but saves the message in a file named after the local part of the first
recipient's address (instead of in
.Va record Ns ).
.
.Mx
.It Ic followupall
Similar to
.Ic followup ,
but responds to all recipients regardless of the
.Va flipr
variable.
.
.Mx
.It Ic followupsender
Similar to
.Ic Followup ,
but responds to the sender only regardless of the
.Va flipr
variable.
.
.Mx
.It Ic Forward
Alias for
.Ic Fwd .
.
.Mx
.It Ic forward
Alias for
.Ic fwd .
.
.Mx
.It Ic from
(f) Takes a list of messages and prints their message headers
(which qualifies this command as \*(UAs search facility).
.
.Mx
.It Ic Fwd
Similar to
.Ic fwd ,
but saves the message in a file named after the local part of the
recipient's address (instead of in
.Va record Ns ).
.
.Mx
.It Ic fwd
Takes a message and the address of a recipient
and forwards the message to him.
The text of the original message is included in the new one,
with the value of the
.Va fwdheading
variable printed before.
The
.Ic fwdignore
and
.Ic fwdretain
commands specify which header fields are included in the new message.
Only the first part of a multipart message is included unless the
.Va forward-as-attachment
option is set.
Unless the option
.Va fullnames
is set recipient addresses will be stripped from comments, names etc.
.
.Mx
.It Ic fwdignore
Specifies which header fields are to be ignored with the command
.Ic fwd .
This command has no effect when the
.Va forward-as-attachment
option is set.
.
.Mx
.It Ic fwdretain
Specifies which header fields are to be retained with the command
.Ic fwd .
.Ic fwdretain
overrides
.Ic fwdignore .
This command has no effect when the
.Va forward-as-attachment
option is set.
.
.Mx
.It Ic ghost
Define or list command aliases, so-called ghosts.
Without arguments a list of all currently known aliases is printed.
With one argument the expansion of the given alias is shown.
With two or more arguments a command alias is defined or updated: the
first argument is the name under which the remaining command line should
be accessible, the content of which can be just about anything.
A ghost can be used everywhere a normal command can be used, but always
takes precedence; any arguments that are given to the command alias are
joined onto the alias content, and the resulting string forms the
command line that is, in effect, executed.
Also see
.Ic unghost .
.Bd -literal -offset indent
? gh xx
`ghost': no such alias: "xx"
? gh xx echo hello,
? gh xx
ghost xx "echo hello,"
? xx
hello,
? xx world
hello, world
.Ed
.
.Mx
.It Ic headers
(h) Show the current group of headers, the size of which depends on
the variable
.Va screen .
If a message-specification is given the group of headers containing the
first message therein is shown and the message at the top of the screen
becomes the new
.Dq dot .
.
.Mx
.It Ic help
(hel) A synonym for
.Ic \&? .
.
.Mx
.It Ic history
\*(OP Either
.Ar show
or
.Ar clear
the list of history entries;
a decimal
.Ar NUMBER
argument selects and shows the respective history entry \(en
press
.Dq ENTER
to accept it, and the history entry will become the new history top.
The default mode if no arguments are given is
.Ar show .
.
.Mx
.It Ic hold
(ho, also
.Ic preserve )
Takes a message list and marks each message therein to be saved in the
user's system mailbox instead of in
.Ev MBOX .
Does not override the
.Ic delete
command.
\*(UA deviates from the POSIX standard with this command, because a
.Ic next
command issued after
.Ic hold
will display the following message, not the current one.
.
.
.Mx
.It Ic if
(i) Part of the nestable
.Ic if Ns / Ns Ic elif Ns / Ns Ic else Ns / Ns Ic endif
conditional execution construct \(em if the given condition is true then
the encapsulated block is executed.
POSIX only supports the conditions
.Ql [Rr]eceive ,
.Ql [Ss]end
and
.Ql [Tt]erm
(execute if standard input is a tty), all remaining conditions are
non-portable extensions; note that falsely specified conditions cause
the execution of the entire conditional construct until the
(matching) closing
.Ic endif
command to be suppressed.
The syntax of the nestable
.Ic if
conditional execution construct requires that each condition and syntax
element is surrounded by whitespace.
.
.Bd -literal -offset indent
if receive
  commands ...
else
  commands ...
endif
.Ed
.
.Pp
Another condition can be any boolean value (see the section
.Sx "Value options"
for booleans) to mark an enwrapped block as
.Dq never execute
or
.Dq always execute .
It is possible to check a variable for existence or compare its
expansion against a user given value or another variable via the
.Ql $
.Pf ( Dq variable next )
conditional trigger character.
The available comparison operators are
.Ql <
(less than),
.Ql <=
(less than or equal to),
.Ql ==
(equal),
.Ql !=
(not equal),
.Ql >=
(greater than or equal to),
.Ql >
(greater than),
.Ql =@
(is substring of) and
.Ql !@
(is not substring of).
The values of the left and right hand side are treated as strings and
are compared 8-bit byte-wise, ignoring case according to the rules of
the US-ASCII encoding (therefore, dependend on the active locale,
possibly producing false results for strings in the locale encoding).
Except for the substring checks the comparison will instead be performed
arithmetically if both, the user given value as well as the variable
content, can be parsed as numbers (integers).
An unset variable is treated as the empty string.
.
.Pp
When the \*(OPal regular expression support is available, the additional
test cases
.Ql =~
and
.Ql !~
can be used.
They treat the right hand side as a regular expression that is matched
case-insensitively and according to the active
.Ev LC_CTYPE
locale, meaning that strings in the locale encoding should be matched
correctly.
.
.Pp
Conditions can be joined via AND-OR lists (where the AND operator is
.Ql &&
and the OR operator is
.Ql || ) ,
which have equal precedence and will be evaluated with left
associativity, thus using the same syntax that is known for the
.Xr sh 1 .
It is also possible to form groups of conditions and lists by enclosing
them in pairs of brackets
.Ql [\ \&.\&.\&.\ ] ,
which may be interlocked within each other, and also be joined via
AND-OR lists.
.
.Pp
The results of individual conditions and entire groups may be modified
via unary operators: the unary operator
.Ql \&!
will reverse the result.
.
.Bd -literal -offset indent
if $debug
  echo *debug* is set
endif
if $ttycharset == "UTF-8"
  echo *ttycharset* is set to UTF-8, case-insensitively
endif
set t1=one t2=one
if $t1 == $t2
  echo These two variables are equal
endif
if $version-major >= 15
  echo Running a new version..
  if $features =@ "regex"
    if $TERM =~ "^xterm\&.*"
      echo ..in an X terminal
    endif
  endif
  if [ [ true ] && [ [ $debug ] || [ $verbose ] ] ]
    echo Noisy, noisy
  endif
  if true && $debug || $verbose
    echo Left associativity, as is known from the shell
  endif
  if ! ! true && ! [ ! $debug && ! $verbose ]
    echo Unary operator support
  endif
endif
.Ed
.
.
.Mx
.It Ic ignore
Without arguments the list of ignored header fields is printed,
otherwise the given list of header fields is added to the ignore list:
Header fields in the ignore list are not printed on the terminal when
a message is printed.
To print a message in its entirety, use the commands
.Ic Type
or
.Ic Print .
Also see
.Ic discard
and
.Ic retain .
.
.Mx
.It Ic imap
\*(OP Sends command strings directly to the current IMAP server.
\*(UA operates always in IMAP `selected state' on the current mailbox;
commands that change this will produce undesirable results and should be
avoided.
Useful IMAP commands are:
.Bl -tag -offset indent -width ".Ic getquotearoot"
.It create
Takes the name of an IMAP mailbox as an argument and creates it.
.It getquotaroot
(RFC 2087) Takes the name of an IMAP mailbox as an argument
and prints the quotas that apply to the mailbox.
Not all IMAP servers support this command.
.It namespace
(RFC 2342) Takes no arguments and prints the Personal Namespaces,
the Other User's Namespaces and the Shared Namespaces.
Each namespace type is printed in parentheses;
if there are multiple namespaces of the same type,
inner parentheses separate them.
For each namespace a prefix and a hierarchy separator is listed.
Not all IMAP servers support this command.
.El
.
.Mx
.It Ic inc
Same as
.Ic newmail .
.
.Mx
.It Ic list
Prints the names of all available commands, alphabetically sorted.
.
.Mx
.It Ic localopts
This command can be used to localize changes to variables, meaning that
their state will be reverted to the former one once the covered scope
is left.
It can only be used inside of macro definition blocks introduced by
.Ic account
or
.Ic define ,
and is interpreted as a boolean (see
.Sx "Value options" ) ;
the
.Dq covered scope
of an account is left once it is switched off again.
.Bd -literal -offset indent
define temporary_settings {
  set global_option1
  localopts on
  set local_option1
  set local_option2
  localopts off
  set global_option2
}
.Ed
.Pp
.Sy Note
that this setting
.Dq stacks up :
i.e., if
.Ql macro1
enables change localization and calls
.Ql macro2 ,
which explicitly resets localization, then any value changes within
.Ql macro2
will still be reverted by
.Ql macro1 !
.
.Mx
.It Ic Lreply
Reply to messages that come in via known
.Pf ( Ic mlist )
or subscribed
.Pf ( Ic mlsubscribe )
mailing lists, or pretend to do so (see
.Sx "Mailing lists" ) :
on top of the usual
.Ic reply
functionality this will actively resort and even remove message
recipients in order to generate a message that is supposed to be send to
a mailing list.
For example it will also implicitly generate a
.Ql Mail-Followup-To:
header if that seems useful, regardless of the setting of the variable
.Va followup-to .
.
.Mx
.It Ic Mail
Similar to
.Ic mail ,
but saves the message in a file named after the local part of the first
recipient's address (instead of in
.Va record Ns ).
.
.Mx
.It Ic mail
(m) Takes a (list of) recipient address(es) as (an) argument(s),
or asks on standard input if none were given;
then collects the remaining mail content and sends it out.
.
.Mx
.It Ic mbox
(mb) The given message list is to be sent to
.Ev MBOX
when \*(UA is quit; this is the default action unless the
.Va hold
option is set.
\*(ID This command can only be used in a system mailbox (see
.Ic file ) .
.
.Mx
.It Ic mimetype
Without any arguments the content of the MIME type cache will displayed.
Otherwise each argument defines a complete MIME type specification of
a type that shall be added (prepended) to the cache.
In any event MIME type sources are loaded first as necessary \(en
.Va mimetypes-load-control
can be used to fine-tune which sources are actually loaded.
Refer to the section on
.Sx "The mime.types files"
for more on MIME type specifications and this topic in general.
MIME type unregistration and cache resets can be triggered with
.Ic unmimetype .
.
.Mx
.It Ic mlist
Without arguments the list of all currently defined mailing lists
(and their attributes, if any) is printed.
Otherwise all given arguments (which need not be quoted except for
whitespace) will be added and henceforth be recognized as mailing lists.
Mailing lists may be removed via the command
.Ic unmlist .
.Pp
If the \*(OPal regular expression support is available then mailing
lists may also be specified as regular expressions (see
.Xr re_format 7
for more on those).
.
.Mx
.It Ic mlsubscribe
Without arguments the list of all currently defined mailing lists which
have a subscription attribute is printed.
Otherwise this attribute will be set for all given mailing lists,
newly creating them as necessary (as via
.Ic mlist ) .
Subscription attributes may be removed via the command
.Ic unmlsubscribe .
Also see
.Va followup-to .
.
.Mx
.It Ic Move
Similar to
.Ic move ,
but moves the messages to a file named after the local part of the
sender address of the first message (instead of in
.Va record Ns ).
.
.Mx
.It Ic move
Acts like
.Ic copy
but marks the messages for deletion if they were transferred
successfully.
.
.Mx
.It Ic More
Like
.Ic more ,
but also prints ignored header fields and all MIME parts.
Identical to
.Ic Page .
.
.Mx
.It Ic more
Invokes the
.Ev PAGER
on the given messages, even in non-interactive mode and as long as the
standard output is a terminal.
Identical to
.Ic page .
.
.Mx
.It Ic netrc
\*(OP Either
.Pf ( Ar show
or)
.Ar clear
the current
.Pa .netrc
cache, loading the file first as necessary in the former case.
Note that \*(UA will try to read the file only once, use
.Ql Ic netrc Ns \:\0\:clear
to unlock the next attempt.
See
.Va netrc-lookup
and the section
.Sx "On URL syntax and credential lookup" ;
the section
.Sx "The .netrc file"
documents the file format in detail.
.
.Mx
.It Ic newmail
Checks for new mail in the current folder without committing any changes
before.
If new mail is present, a message is printed.
If the
.Va header
variable is set,
the headers of each new message are also printed.
.
.Mx
.It Ic next
(n) (like
.Ql +
or
.Dq ENTER )
Goes to the next message in sequence and types it.
With an argument list, types the next matching message.
.
.Mx
.It Ic New
Same as
.Ic Unread .
.
.Mx
.It Ic new
Same as
.Ic unread .
.
.Mx
.It Ic noop
If the current folder is accessed via a network connection, a
.Dq NOOP
command is sent, otherwise no operation is performed.
.
.Mx
.It Ic Page
Like
.Ic page ,
but also prints ignored header fields and all MIME parts.
Identical to
.Ic More .
.
.Mx
.It Ic page
Invokes the
.Ev PAGER
on the given messages, even in non-interactive mode and as long as the
standard output is a terminal.
Identical to
.Ic more .
.
.Mx
.It Ic Pipe
Like
.Ic pipe
but also pipes ignored header fields and all parts of MIME
.Ql multipart/alternative
messages.
.
.Mx
.It Ic pipe
(pi) Takes a message list and a shell command
and pipes the messages through the command.
Without an argument the current message is piped through the command
given by the
.Va cmd
variable.
If the
.Va page
variable is set,
every message is followed by a formfeed character.
.
.Mx
.It Ic preserve
(pre) A synonym for
.Ic hold .
.
.Mx
.It Ic Print
(P) Like
.Ic print
but also prints out ignored header fields and all parts of MIME
.Ql multipart/alternative
messages.
See also
.Ic print ,
.Ic ignore
and
.Ic retain .
.
.Mx
.It Ic print
(p) Takes a message list and types out each message on the user's
terminal.
For MIME multipart messages, all parts with a content type of
.Ql text
or
.Ql message
are shown, the other are hidden except for their headers.
Messages are decrypted and converted to the terminal character set
if necessary.
.
.Mx
.It Ic quit
(q) Terminates the session, saving all undeleted, unsaved messages in
the current
.Ev MBOX ,
preserving all messages marked with
.Ic hold
or
.Ic preserve
or never referenced in the system mailbox,
and removing all other messages from the system mailbox.
If new mail has arrived during the session,
the message
.Dq You have new mail
will be shown.
If given while editing a mailbox file with the command line flag
.Fl f ,
then the edit file is rewritten.
A return to the shell is effected,
unless the rewrite of edit file fails,
in which case the user can escape with the exit command.
.
.Mx
.It Ic redirect
Same as
.Ic resend .
.
.Mx
.It Ic Redirect
Same as
.Ic Resend .
.
.Mx
.It Ic remove
Removes the named folders.
The user is asked for confirmation in interactive mode.
.
.Mx
.It Ic rename
Takes the name of an existing folder
and the name for the new folder
and renames the first to the second one.
Both folders must be of the same type
and must be located on the current server for IMAP.
.
.Mx
.It Ic Reply
(R) Reply to originator.
Does not reply to other recipients of the original message.
.Va flipr
will exchange this command with
.Ic reply .
Unless the option
.Va fullnames
is set the recipient address will be stripped from comments, names etc.
.
.Mx
.It Ic reply
(r) Take a message and group-responds to it by addressing the sender
and all recipients.
.Va followup-to ,
.Va followup-to-honour ,
.Va reply-to-honour
as well as
.Va recipients-in-cc
influence response behaviour.
The command
.Ic Lreply
offers special support for replying to mailing lists.
Unless the option
.Va fullnames
is set recipient addresses will be stripped from comments, names etc.
If
.Va flipr
is set the commands
.Ic Reply
and
.Ic reply
are exchanged.
.
.Mx
.It Ic replyall
Similar to
.Ic reply ,
but initiates a group-reply regardless of the value of
.Va flipr .
.
.Mx
.It Ic replysender
Similar to
.Ic Reply ,
but responds to the sender only regardless of the value of
.Va flipr .
.
.Mx
.It Ic Resend
Like
.Ic resend ,
but does not add any header lines.
This is not a way to hide the sender's identity,
but useful for sending a message again to the same recipients.
.
.Mx
.It Ic resend
Takes a list of messages and a user name
and sends each message to the named user.
.Ql Resent-From:
and related header fields are prepended to the new copy of the message.
.
.Mx
.It Ic Respond
Same as
.Ic Reply .
.
.Mx
.It Ic respond
Same as
.Ic reply .
.
.Mx
.It Ic respondall
Same as
.Ic replyall .
.
.Mx
.It Ic respondsender
Same as
.Ic replysender .
.
.Mx
.It Ic retain
(ret) Without arguments the list of retained header fields is printed,
otherwise the given list of header fields is added to the retain list:
Header fields in the retain list are shown on the terminal when
a message is printed, all other header fields are suppressed.
To print a message in its entirety, use the commands
.Ic Type
or
.Ic Print .
Also see
.Ic discard
and
.Ic ignore ;
.Ic retain
takes precedence over the mentioned.
.
.Mx
.It Ic Save
(S) Similar to
.Ic save,
but saves the messages in a file named after the local part of the
sender of the first message instead of (in
.Va record
and) taking a filename argument.
.
.Mx
.It Ic save
(s) Takes a message list and a filename and appends each message in turn
to the end of the file.
If no filename is given, the
.Ev MBOX
file is used.
The filename in quotes, followed by the generated character count
is echoed on the user's terminal.
If editing a system mailbox the messages are marked for deletion.
Compressed files and IMAP mailboxes are handled as described for the
.Fl f
command line option above.
.
.Mx
.It Ic savediscard
Same as
.Ic saveignore .
.
.Mx
.It Ic saveignore
Is to
.Ic save
what
.Ic ignore
is to
.Ic print
and
.Ic type .
Header fields thus marked are filtered out when saving a message by
.Ic save
or when automatically saving to
.Ev MBOX .
This command should only be applied to header fields that do not contain
information needed to decode the message,
as MIME content fields do.
If saving messages on an IMAP account ignoring fields makes it
impossible to copy the data directly on the server,
thus operation usually becomes much slower.
.
.Mx
.It Ic saveretain
Is to
.Ic save
what
.Ic retain
is to
.Ic print
and
.Ic type .
Header fields thus marked are the only ones saved with a message when
saving by
.Ic save
or when automatically saving to
.Ev MBOX .
.Ic saveretain
overrides
.Ic saveignore .
The use of this command is strongly discouraged since it may strip
header fields that are needed to decode the message correctly.
.
.Mx
.It Ic seen
Takes a message list and marks all messages as having been read.
.
.Mx
.It Ic set
(se) Without arguments this command prints all options and, for
non-binary options, values that are currently known to \*(UA.
Setting any of the options
.Va bsdcompat
or
.Va bsdset
changes the output format to BSD style, otherwise a properly quoted
listing is produced.
If
.Va debug
is set or
.Va verbose
has been set twice then the listing is modified to mark out assembled
variables.
.Pp
Otherwise modifies (set and unsets) the given options.
Arguments are of the form
.Ql option=value
(no space before or after
.Ql = ) ,
or plain
.Ql option
if there is no value.
Quotation marks may be placed around any part of the assignment
statement to quote blanks or tabs, e.g.,
.Pp
.Dl set indentprefix="->"
.Pp
If an argument begins with
.Ql no ,
as in
.Ql set nosave ,
the effect is the same as invoking the
.Ic unset
command with the remaining part of the variable
.Pf ( Ql unset save ) .
.
.Mx
.It Ic setenv
Identical to
.Ic set
except that the options are also exported into the program environment;
since this task requires native host support the command will always
report error if that is not available (but still act like
.Ic set
in this case).
This operation is a no-op unless all resource files have been loaded.
Also see
.Ic unsetenv .
.
.Mx
.It Ic shell
(sh) Invokes an interactive version of the shell.
.
.Mx
.It Ic shortcut
Without arguments the list of all currently defined shortcuts is
printed.
Otherwise all given arguments (which need not be quoted except for
whitespace) are treated as pairs of shortcuts and their expansions,
creating new or changing already existing shortcuts, as necessary.
Shortcuts may be removed via the command
.Ic unshortcut .
The expansion strings should be in the syntax that has been described
for the
.Ic file
command.
.
.Mx
.It Ic show
Like
.Ic print ,
but performs neither MIME decoding nor decryption, so that the raw
message text is shown.
.
.Mx
.It Ic size
(si) Print the size in characters of each message of the given
message-list.
.
.Mx
.It Ic sort
Create a sorted representation of the current folder,
and change the
.Ic next
command and the addressing modes such that they refer to messages in the
sorted order.
Message numbers are the same as in regular mode.
If the
.Va header
variable is set,
a header summary in the new order is also printed.
Possible sorting criteria are:
.Pp
.Bl -tag -compact -offset indent -width "subject"
.It date
Sort the messages by their
.Ql Date:
field, that is by the time they were sent.
.It from
Sort messages by the value of their
.Ql From:
field, that is by the address of the sender.
If the
.Va showname
variable is set, the sender's real name (if any) is used.
.It size
Sort the messages by their size.
.It spam
\*(OP Sort the message by their spam score, as has been classified by
.Ic spamrate .
.It status
Sort the messages by their message status.
.It subject
Sort the messages by their subject.
.It thread
Create a threaded display.
.It to
Sort messages by the value of their
.Ql To:
field, that is by the address of the recipient.
If the
.Va showname
variable is set, the recipient's real name (if any) is used.
.El
.Pp
If no argument is given,
the current sorting criterion is printed.
.
.Mx
.It Ic source
(so) The source command reads commands from a file.
.
.Mx
.It Ic source_if
The difference to
.Ic source
is that this command will not generate an error if the given file
argument cannot be opened successfully.
This can matter in, e.g., resource files, since loading of those is
stopped when an error is encountered.
.
.Mx
.It Ic spamclear
\*(OP Takes a list of messages and clears their
.Ql is-spam
flag.
.
.Mx
.It Ic spamforget
\*(OP Takes a list of messages and causes the
.Va spam-interface
to forget it has ever used them to train its Bayesian filter.
Unless otherwise noted the
.Ql is-spam
flag of the message is inspected to chose whether a message shall be
forgotten to be
.Dq ham
or
.Dq spam .
.
.Mx
.It Ic spamham
\*(OP Takes a list of messages and informs the Bayesian filter of the
.Va spam-interface
that they are
.Dq ham .
This also clears the
.Ql is-spam
flag of the messages in question.
.
.Mx
.It Ic spamrate
\*(OP Takes a list of messages and rates them using the configured
.Va spam-interface ,
without modifying the messages, but setting their
.Ql is-spam
flag as appropriate; because the spam rating headers are lost the rate
will be forgotten once the mailbox is left.
Refer to the manual section
.Sx "Handling spam"
for the complete picture of spam handling in \*(UA.
.
.Mx
.It Ic spamset
\*(OP Takes a list of messages and sets their
.Ql is-spam
flag.
.
.Mx
.It Ic spamspam
\*(OP Takes a list of messages and informs the Bayesian filter of the
.Va spam-interface
that they are
.Dq spam .
This also sets the
.Ql is-spam
flag of the messages in question.
.
.Mx
.It Ic thread
\*(OB The same as
.Ql sort thread
(consider using a
.Ql ghost
as necessary).
Create a threaded representation of the current folder,
i.\|e. indent messages that are replies to other messages in the header
display and change the
.Ic next
command and the addressing modes such that they refer to messages in the
threaded order.
Message numbers are the same as in unthreaded mode.
If the
.Va header
variable is set,
a header summary in threaded order is also printed.
.
.Mx
.It Ic top
(to) Takes a message list and prints the top few lines of each.
The number of lines printed is controlled by the variable
.Va toplines
and defaults to five.
.
.Mx
.It Ic touch
(tou) Takes a message list and marks the messages for saving in
.Ev MBOX .
\*(UA deviates from the POSIX standard with this command,
as a following
.Ic next
command will display the following message instead of the current one.
.
.Mx
.It Ic Type
(T) Identical to the
.Ic Print
command.
.
.Mx
.It Ic type
(t) A synonym for
.Ic print .
.
.Mx
.It Ic unaccount
Delete all given accounts.
An error message is printed if a given account is not defined.
The special name
.Ql *
will discard all existing accounts.
.
.Mx
.It Ic unalias
(una) Takes a list of names defined by alias commands
and discards the remembered groups of users.
The special name
.Ql *
will discard all existing aliases.
.
.Mx
.It Ic unanswered
Takes a message list and marks each message as not having been answered.
.
.Mx
.It Ic uncollapse
Only applicable to threaded mode.
Takes a message list and makes the message and all replies to it visible
in header summaries again.
When a message becomes the current message,
it is automatically made visible.
Also when a message with collapsed replies is printed,
all of these are automatically uncollapsed.
.
.Mx
.It Ic undefine
Undefine all given macros.
An error message is printed if a given macro is not defined.
The special name
.Ql *
will discard all existing macros.
.
.Mx
.It Ic undelete
(u) Takes a message list and marks each message as not being deleted.
.
.Mx
.It Ic undraft
Takes a message list and
.Pf un Ic draft Ns
s each message.
.
.Mx
.It Ic unflag
Takes a message list and marks each message as not being
.Ic flag Ns ged .
.
.Mx
.It Ic unfwdignore
Removes the header field names from the list of ignored fields for the
.Ic forward
command.
The special name
.Ql *
will remove all fields.
.
.Mx
.It Ic unfwdretain
Removes the header field names from the list of retained fields for the
.Ic forward
command.
The special name
.Ql *
will remove all fields.
.
.Mx
.It Ic unghost
Remove all the given command
.Ic ghost Ns s Ns .
The special name
.Ql *
will remove all ghosts.
.
.Mx
.It Ic unignore
Removes the header field names from the list of ignored fields.
The special name
.Ql *
will remove all fields.
.
.Mx
.It Ic unmimetype
Delete all given MIME types, e.g.,
.Ql unmimetype text/plain
will remove all registered specifications for the MIME type
.Ql text/plain .
The special name
.Ql *
will discard all existing MIME types, just as will
.Ql reset ,
but which also reenables cache initialization via
.Va mimetypes-load-control .
.
.Mx
.It Ic unmlist
Forget about all the given mailing lists.
The special name
.Ql *
will remove all lists.
Also see
.Ic mlist .
.
.Mx
.It Ic unmlsubscribe
Remove the subscription attribute from all given mailing lists.
The special name
.Ql *
will clear the attribute from all lists which have it set.
Also see
.Ic mlsubscribe .
.
.Mx
.It Ic Unread
Same as
.Ic unread .
.
.Mx
.It Ic unread
Takes a message list and marks each message as not having been read.
.
.Mx
.It Ic unretain
Removes the header field names from the list of retained fields.
The special name
.Ql *
will remove all fields.
.
.Mx
.It Ic unsaveignore
Removes the header field names from the list of ignored fields for
saving.
The special name
.Ql *
will remove all fields.
.
.Mx
.It Ic unsaveretain
Removes the header field names from the list of retained fields for
saving.
The special name
.Ql *
will remove all fields.
.
.Mx
.It Ic unset
(uns) Takes a list of option names and discards their remembered values;
the inverse of
.Ic set .
.
.Mx
.It Ic unsetenv
Identical to
.Ic unset
except that the options are also removed from the program environment;
since this task requires native host support the command will always
report error if that is not available (but still act like
.Ic unset Ns
).
This operation is a no-op unless all resource files have been loaded.
Also see
.Ic setenv .
.
.Mx
.It Ic unshortcut
Deletes the shortcut names given as arguments.
The special name
.Ql *
will remove all shortcuts.
.
.Mx
.It Ic unsort
Disable sorted or threaded mode
(see the
.Ic sort
and
.Ic thread
commands),
return to normal message order and,
if the
.Va header
variable is set,
print a header summary.
.
.Mx
.It Ic unthread
\*(OB
Same as
.Ic unsort .
.
.Mx
.It Ic urldecode
Decode the given URL-encoded string arguments and show the results.
.
.Mx
.It Ic urlencode
URL-encode the given arguments and show the results.
.
.Mx
.It Ic varedit
Edit the values of or create the given variable(s) in the
.Ev EDITOR .
Binary variables cannot be edited.
.
.Mx
.It Ic varshow
Show informations about all the given options.
\*(UA knows about a finite set of known builtin variables that are
subdivided further in binary and value variants;
they may have special properties, like
.Dq read-only
(setting may not be changed) and
.Dq virtual ,
meaning that the value is generated on-the-fly as necessary.
Beside those known variables an infinite number of unknown, so-called
.Dq assembled
variables, which are expected to be able to store values, may exist.
.Bd -literal -offset indent
? set foo=bar nobar
? varshow sendwait version-major foo bar
"sendwait": (73) binary: set=1 (ENVIRON=0)
"version-major": (192) value, read-only, virtual:\e
  set=1 (ENVIRON=0) value<14>
"foo": (assembled) set=1 (ENVIRON=0) value<bar>
"bar": (assembled) set=0 (ENVIRON=0) value<NULL>
.Ed
.
.Mx
.It Ic verify
\*(OP Takes a message list and verifies each message.
If a message is not a S/MIME signed message,
verification will fail for it.
The verification process checks if the message was signed using a valid
certificate,
if the message sender's email address matches one of those contained
within the certificate,
and if the message content has been altered.
.
.Mx
.It Ic visual
(v) Takes a message list and invokes the display editor on each message.
Modified contents are discarded unless the
.Va writebackedited
variable is set.
.
.Mx
.It Ic write
(w) For conventional messages the body without all headers is written.
The original message is never marked for deletion in the originating
mail folder.
The output is decrypted and converted to its native format as necessary.
If the output file exists, the text is appended.
If a message is in MIME multipart format its first part is written to
the specified file as for conventional messages, handling of the remains
depends on the execution mode.
No special handling of compressed files is performed.
.Pp
In interactive mode the user is consecutively asked for the filenames of
the processed parts.
For convience saving of each part may be skipped by giving an empty
value, the same result as writing it to
.Pa /dev/null .
Shell piping the part content by specifying a leading vertical bar
.Ql |
character for the filename is supported.
Other user input is expanded as usually for folders, e.g., tilde
expansion is performed, and contents of the destination file are
overwritten if the file previously existed.
.Pp
\*(ID In non-interactive mode any part which does not specify a filename
is ignored, and suspicious parts of filenames of the remaining parts are
URL percent encoded (as via
.Ic urlencode )
to prevent injection of malicious character sequences, resulting in
a filename that will be written into the current directory.
Existing files won't be overwritten, instead the part number or
a dot are appended after a number sign
.Ql #
to the name until file creation succeeds (or fails due to other
reasons).
.
.Mx
.It Ic xit
(x) A synonym for
.Ic exit .
.
.Mx
.It Ic z
\*(UA presents message headers in
.Va screen Ns
fuls as described under the
.Ic headers
command.
Without arguments this command scrolls to the next window of messages,
likewise if the argument is
.Ql + .
An argument of
.Ql -
scrolls to the last,
.Ql ^
scrolls to the first, and
.Ql $
to the last
.Va \&\&screen
of messages.
A number argument prefixed by
.Ql +
or
.Ql \-
indicates that the window is calculated in relation to the current
position, and a number without a prefix specifies an absolute position.
.
.Mx
.It Ic Z
Similar to
.Ic z ,
but scrolls to the next or previous window that contains at least one
.Ql new
or
.Ic flag Ns
ged message.
.El
.\" }}}
.
.
.\" .Sh TILDE ESCAPES {{{
.Sh "TILDE ESCAPES"
.
Here is a summary of the tilde escapes,
which are used to perform special functions when composing messages.
Tilde escapes are only recognized at the beginning of lines.
The name
.Dq tilde escape
is somewhat of a misnomer since the actual escape character can be
changed by adjusting the option
.Va escape .
.
.Bl -tag -width ".Ic __ filename"
.Mx
.It Ic ~~ Ar string
Insert the string of text in the message prefaced by a single
.Ql ~ .
(If the escape character has been changed,
that character must be doubled
in order to send it at the beginning of a line.)
.
.Mx
.It Ic ~! Ar command
Execute the indicated shell
.Ar command ,
then return to the message.
.
.Mx
.It Ic ~.
Same effect as typing the end-of-file character.
.
.Mx
.It Ic ~: Ar \*(UA-command Ns \0or Ic ~_ Ar \*(UA-command
Execute the given \*(UA command.
Not all commands, however, are allowed.
.
.Mx
.It Ic ~?
Write a summary of command escapes.
.
.Mx
.It Ic ~< Ar filename
Identical to
.Ic ~r .
.
.Mx
.It Ic ~<! Ar command
.Ar command
is executed using the shell.
Its standard output is inserted into the message.
.
.Mx
.It Ic ~@ Op Ar filename...
With no arguments, edit the attachment list interactively.
If an attachment's file name is left empty,
that attachment is deleted from the list.
When the end of the attachment list is reached,
\*(UA will ask for further attachments until an empty name is given.
If a given file name solely consists of the number sign
.Ql #
followed by a valid message number of the currently active mailbox, then
the given message is attached as a MIME
.Ql message/rfc822
and the rest of this section does not apply.
.Pp
If character set conversion has been compiled into \*(UA, then this mode
gives the user the option to specify input and output character sets,
unless the file extension indicates binary content, in which case \*(UA
asks whether this step shall be skipped for the attachment in question.
If not skipped, then the charset that succeeds to represent the
attachment data will be used in the
.Ql charset=
MIME parameter of the mail message:
.Pp
.Bl -bullet -compact
.It
If input and output character sets are specified, then the conversion is
performed on the fly.
The user will be asked repeatedly until the desired conversion succeeds.
.It
If only an output character set is specified, then the input is assumed
to be in the
.Va ttycharset
charset and will be converted to the given output charset on the fly.
The user will be asked repeatedly until the desired conversion succeeds.
.It
If no character sets are specified at all then the algorithm that is
documented in the section
.Sx "Character sets"
is applied, but directly and on the fly.
The user will be asked repeatedly until the desired conversion succeeds.
.It
Finally, if an input-, but no output character set is specified, then no
conversion is ever performed, but the
.Ql charset=
MIME parameter value will still be set to the user input.
.It
The character set selection loop can be left by typing
.Ql control-C ,
i.e., causing an interrupt.
.\" \*(OU next sentence
Note that before \*(UA version 15.0 this terminates the entire
current attachment selection, not only the character set selection.
.El
.Pp
Without character set conversion support, \*(UA will ask for the input
character set only, and it'll set the
.Ql charset=
MIME parameter value to the given input, if any;
if no user input is seen then the
.Va ttycharset
character set will be used for the parameter value instead.
Note that the file extension check isn't performed in this mode, since
no conversion will take place anyway.
.Pp
Note that in non-interactive mode, for reproduceabilities sake, there
will always be two questions for each attachment, regardless of whether
character set conversion is available and what the file extension is.
The first asks for the filename, and the second asks for the input
character set to be passed through to the corresponding MIME parameter;
no conversion will be tried if there is input to the latter question,
otherwise the usual conversion algorithm, as above, is applied.
For message attachments, the answer to the second question is completely
ignored.
.Pp
If (instead)
.Ar filename
arguments are specified for the
.Ic \&\&~@
command they are treated as a comma separated list of files,
which are all expanded and appended to the end of the attachment list.
(Filenames with commas, or with leading or trailing whitespace can only
be added via the command line or the first method.
Message attachments can only be added via the first method;
filenames which clash with message numbers can only be added via the
command line or the second method.)
In this mode the (text) attachments are assumed to be in
.Va ttycharset
encoding, and will be evaluated as documented in the section
.Sx "Character sets" .
.
.Mx
.It Ic ~A
Inserts the string contained in the
.Va Sign
variable (same as
.Ql Ic ~i Ns \0Sign ) .
The escape sequences tabulator
.Ql \et
and newline
.Ql \en
are understood.
.
.Mx
.It Ic ~a
Inserts the string contained in the
.Va sign
variable (same as
.Ql Ic ~i Ns \0sign ) .
The escape sequences tabulator
.Ql \et
and newline
.Ql \en
are understood.
.
.Mx
.It Ic ~b Ar name ...
Add the given names to the list of blind carbon copy recipients.
.
.Mx
.It Ic ~c Ar name ...
Add the given names to the list of carbon copy recipients.
.
.Mx
.It Ic ~d
Read the file specified by the
.Ev DEAD
variable into the message.
.
.Mx
.It Ic ~e
Invoke the text editor on the message collected so far.
After the editing session is finished,
the user may continue appending text to the message.
.
.Mx
.It Ic ~F Ar messages
Read the named messages into the message being sent, including all
message headers and MIME parts.
If no messages are specified, read in the current message.
.
.Mx
.It Ic ~f Ar messages
Read the named messages into the message being sent.
If no messages are specified, read in the current message.
.Ic ignore
and
.Ic retain
lists are used to modify the message headers.
For MIME multipart messages,
only the first printable part is included.
.
.Mx
.It Ic ~H
Edit the message header fields
.Ql From: ,
.Ql Reply-To: ,
.Ql Sender:
and
.Ql Organization:
by typing each one in turn and allowing the user to edit the field.
The default values for these fields originate from the
.Va from , replyto , sender
and
.Va ORGANIZATION
variables.
.
.Mx
.It Ic ~h
Edit the message header fields
.Ql To: ,
.Ql Cc: ,
.Ql Bcc:
and
.Ql Subject:
by typing each one in turn and allowing the user to edit the field.
.
.Mx
.It Ic ~i Ar variable
Insert the value of the specified variable into the message,
adding a newline character at the end.
The message remains unaltered if the variable is unset or empty.
The escape sequences tabulator
.Ql \et
and newline
.Ql \en
are understood.
.
.Mx
.It Ic ~M Ar messages
Read the named messages into the message being sent,
indented by
.Va indentprefix .
If no messages are specified, read the current message.
.
.Mx
.It Ic ~m Ar messages
Read the named messages into the message being sent,
indented by
.Va indentprefix .
If no messages are specified, read the current message.
.Ic ignore
and
.Ic retain
lists are used to modify the message headers.
For MIME multipart messages,
only the first printable part is included.
.
.Mx
.It Ic ~p
Print out the message collected so far,
prefaced by the message header fields
and followed by the attachment list, if any.
.
.Mx
.It Ic ~q
Abort the message being sent,
copying it to the file specified by the
.Ev DEAD
variable if
.Va save
is set.
.
.Mx
.It Ic ~R Ar filename
Read the named file into the message, indented by
.Va indentprefix .
.
.Mx
.It Ic ~r Ar filename
Read the named file into the message.
.
.Mx
.It Ic ~s Ar string
Cause the named string to become the current subject field.
.
.Mx
.It Ic ~t Ar name ...
Add the given name(s) to the direct recipient list.
.
.Mx
.It Ic ~U Ar messages
Read in the given / current message(s) excluding all headers, indented by
.Va indentprefix .
.
.Mx
.It Ic ~u Ar messages
Read in the given / current message(s), excluding all headers.
.
.Mx
.It Ic ~v
Invoke an alternate editor (defined by the
.Ev VISUAL
option) on the message collected so far.
Usually, the alternate editor will be a screen editor.
After the editor is quit,
the user may resume appending text to the end of the message.
.
.Mx
.It Ic ~w Ar filename
Write the message onto the named file.
If the file exists,
the message is appended to it.
.
.Mx
.It Ic ~x
Same as
.Ic ~q ,
except that the message is not saved at all.
.
.Mx
.It Ic ~| Ar command
Pipe the message through the specified filter command.
If the command gives no output or terminates abnormally,
retain the original text of the message.
E.g., the command
.Xr fmt 1
is often used as a rejustifying filter.
.El
.\" }}}
.
.
.\" .Sh VARIABLE OPTIONS {{{
.Sh "VARIABLE OPTIONS"
.
Variables are controlled via
.Ic set
and
.Ic unset
commands; in general using
.Ic unset
can also be accomplished by prefixing a variable name with the string
.Dq no
and calling
.Ic set ,
e.g.,
.Ql unset crt
will have the same effect as
.Ql set nocrt .
Creation or editing of variables in an editor can also be achieved with
.Ic varedit .
.Ic varshow
will give more insight on the given variable(s), whereas
.Ic set
will print a listing of all variables when called without arguments.
Options are also implicitly inherited from the program
.Sx ENVIRONMENT
and can be set explicitly via the command line option
.Fl S .
.
.Pp
Different kind of options exist:
binary options, which can only be in one of the two states
.Dq set
and
.Dq unset ,
as well as value options which have an assigned string value, for which
proper quoting may be important upon assignment time.
.
.\" .Ss "Initial settings" {{{
.\" (Keep in sync: ./main.c:_startup(), ./nail.rc, ./nail.1:"Initial settings"!)
.Ss "Initial Settings"
.
The standard POSIX 2008/Cor 1-2013 mandates the following initial
variable settings:
.Pf no Va allnet ,
.Pf no Va append ,
.Va asksub ,
.Pf no Va askbcc ,
.Pf no Va autoprint ,
.Pf no Va bang ,
.Pf no Va cmd ,
.Pf no Va crt ,
.Pf no Va debug ,
.Pf no Va dot ,
.Va escape
set to
.Ql ~ ,
.Pf no Va flipr ,
.Pf no Va folder ,
.Va header ,
.Pf no Va hold ,
.Pf no Va ignore ,
.Pf no Va ignoreeof ,
.Pf no Va keep ,
.Pf no Va keepsave ,
.Pf no Va metoo ,
.Pf no Va outfolder ,
.Pf no Va page ,
.Va prompt
set to
.Ql ?\0
(note that \*(UA deviates from the standard by using
.Ql \e&\0 ,
but the
.Ql \e&
special prompt escape results in
.Dq \&?
being printed unless
.Va bsdcompat
is set),
.Pf no Va quiet ,
.Pf no Va record ,
.Va save ,
.Pf no Va sendwait ,
.Pf no Va showto ,
.Pf no Va Sign ,
.Pf no Va sign ,
.Va toplines
set to
.Ql 5 .
.
.Pp
Notes: \*(UA doesn't support the
.Pf no Va onehop
variable \(en use command line options or
.Va sendmail-arguments
to pass options through to a MTA.
And the default global
.Pa \*(UR
file (which is loaded unless the
.Fl n
command line flag has been used or the
.Ev NAIL_NO_SYSTEM_RC
environment variable is set) bends those initial settings a bit, e.g.,
it sets the options
.Va hold ,
.Va keepsave
and
.Va keep ,
to name a few, calls
.Ic retain
etc., and should thus be taken into account.
.\" }}}
.
.\" .Ss "Binary options" {{{
.Ss "Binary options"
.
.Bl -tag -width ".Va _utoprin_"
.Mx
.It Va add-file-recipients
When file or pipe recipients have been specified,
mention them in the corresponding address fields of the message instead
of silently stripping them from their recipient list.
By default such addressees are not mentioned.
.
.Mx
.It Va allnet
Causes only the local part to be evaluated
when comparing addresses.
.
.Mx
.It Va append
Causes messages saved in
.Ev MBOX
to be appended to the end rather than prepended.
This should always be set.
.
.Mx
.Mx
.It Va ask Ns \0or Va asksub
Causes \*(UA to prompt for the subject of each message sent.
If the user responds with simply a newline,
no subject field will be sent.
.
.Mx
.It Va askatend
Causes the prompts for
.Ql Cc:
and
.Ql Bcc:
lists to appear after the message has been edited.
.
.Mx
.It Va askattach
If set, \*(UA asks for files to attach at the end of each message, shall
the list be found empty at that time.
An empty line finalizes the list.
.
.Mx
.It Va askcc
Causes the user to be prompted for carbon copy recipients
(at the end of each message if
.Va askatend
or
.Va bsdcompat
are set) shall the list be found empty (at that time).
An empty line finalizes the list.
.
.Mx
.It Va askbcc
Causes the user to be prompted for blind carbon copy
recipients (at the end of each message if
.Va askatend
or
.Va bsdcompat
are set) shall the list be found empty (at that time).
An empty line finalizes the list.
.
.Mx
.It Va asksign
\*(OP Causes the user to be prompted if the message is to be signed at
the end of each message.
The
.Va smime-sign
variable is ignored when this variable is set.
.
.Mx
.It Va autocollapse
Causes threads to be collapsed automatically when threaded mode is
entered (see the
.Ic collapse
command).
.
.Mx
.It Va autoprint
Causes the delete command to behave like
.Ql dp - ;
thus, after deleting a message the next one will be typed automatically.
.
.Mx
.It Va autothread
\*(OB Causes threaded mode (see the
.Ic thread
command) to be entered automatically when a folder is opened.
The same as
.Ql autosort=thread .
.
.Mx
.It Va bang
Enables the substitution of
.Ql \&!
by the contents of the last command line in shell escapes.
.
.Mx
.It Va batch-exit-on-error
If the batch mode has been enabled via the
.Fl #
command line option, then this variable will be consulted whenever \*(UA
completes one operation (returns to the command prompt); if it is set
then \*(UA will terminate if the last operation generated an error.
.
.Mx
.It Va bsdannounce
Causes automatic display of a header summary after executing a
.Ic file
command.
.
.Mx
.It Va bsdcompat
Sets some cosmetical features to traditional BSD style;
has the same affect as setting
.Va askatend
and all other variables prefixed with
.Ql bsd ;
it also changes the meaning of the \*(UA specific
.Ql \e&
.Va prompt
escape sequence.
.
.Mx
.It Va bsdflags
Changes the letters printed in the first column of a header summary
to traditional BSD style.
.
.Mx
.It Va bsdheadline
Changes the display of columns in a header summary to traditional BSD
style.
.
.Mx
.It Va bsdmsgs
Changes some informational messages to traditional BSD style.
.
.Mx
.It Va bsdorder
Causes the
.Ql Subject:
field to appear immediately after the
.Ql To:
field in message headers and with the
.Ic ~h
.Sx "TILDE ESCAPES" .
.
.Mx
.It Va bsdset
Changes the output format of the
.Ic set
command to traditional BSD style.
.
.Mx
.It Va colour-disable
\*(OP Forcefully disable usage of colours.
Also see the section
.Sx "Coloured message display" .
.
.Mx
.It Va colour-pager
\*(OP Whether colour shall be used for output that is paged through
.Ev PAGER .
Note that pagers may need special flags, e.g.,
.Xr less 1
requires the option
.Fl \&\&R
and
.Xr lv 1
the option
.Fl \&\&c
in order to support colours; therefore \*(UA will inspect the variable
.Ev PAGER
\(en if that starts with the string
.Dq less
a non-existing environment variable
.Va LESS
will be set to
.Ql FRSXi ,
likewise for
.Dq lv
.Va LV
will optionally be set to
.Dq -c .
Also see the section
.Sx "Coloured message display"
for more on this.
.
.Mx
.It Va debug
Prints debugging messages and disables the actual delivery of messages.
Also implies
.Pf no Va record
and
.Pf no Va save .
.
.Mx
.It Va disconnected
\*(OP When an IMAP mailbox is selected and this variable is set,
no connection to the server is initiated.
Instead, data is obtained from the local cache (see
.Va imap-cache Ns
).
Mailboxes that are not present in the cache
and messages that have not yet entirely been fetched from the server
are not available;
to fetch all messages in a mailbox at once,
the command
.No ` Ns Li copy * /dev/null Ns '
can be used while still in connected mode.
Changes that are made to IMAP mailboxes in disconnected mode are queued
and committed later when a connection to that server is made.
This procedure is not completely reliable since it cannot be guaranteed
that the IMAP unique identifiers (UIDs) on the server still match the
ones in the cache at that time.
Data is saved to
.Ev DEAD
when this problem occurs.
.
.It Va disconnected-USER@HOST
The specified account is handled as described for the
.Va disconnected
variable above,
but other accounts are not affected.
.
.Mx
.It Va disposition-notification-send
\*(OP Emit a
.Ql Disposition-Notification-To:
header (RFC 3798) with the message.
This requires a set
.Va from
variable.
.\" TODO .It Va disposition-notification-send-HOST
.\"Overrides
.\".Va disposition-notification-send
.\" for SMTP accounts on a specific host.
.\" TODO .It Va disposition-notification-send-USER@HOST
.\"Overrides
.\".Va disposition-notification-send
.\"for a specific account.
.
.Mx
.It Va dot
When dot is set, a dot
.Ql \&.
on a line by itself during message input from a terminal shall be
treated as end-of-message (in addition to the normal end-of-file
condition).
If
.Va ignoreeof
is set
.Pf no Va dot
is ignored and using a dot is the only method to terminate input mode.
.
.Mx
.It Va dotlock-ignore-error
\*(OP Synchronization of mailboxes which \*(UA treats as system
mailboxes (see the command
.Ic file )
will be protected with so-called dotlock files\(emthe traditional mail
spool file locking method\(emin addition to system file locking.
Because \*(UA ships with a privilege-separated dotlock creation program
that should always be able to create such a dotlock file there is no
good reason to ignore dotlock file creation errors, and thus these are
fatal unless this variable is set.
.
.Mx
.It Va editalong
If this variable is set then the editor is started automatically when
a message is composed in interactive mode, as if the
.Ic ~e
.Sx "TILDE ESCAPES"
had been specified.
The
.Va editheaders
variable is implied for this automatically spawned editor session.
.
.Mx
.It Va editheaders
When a message is edited while being composed,
its header is included in the editable text.
The
.Ql To: ,
.Ql Cc: ,
.Ql Bcc: ,
.Ql Subject: ,
.Ql From: ,
.Ql Reply-To: ,
.Ql Sender: ,
and
.Ql Organization:
fields are accepted within the header, other fields are ignored.
.
.Mx
.It Va emptystart
If the mailbox is empty \*(UA normally prints
.Dq \&No mail for user
and exits immediately.
If this option is set \*(UA starts even with an empty mailbox.
.
.Mx
.It Va flipr
This option reverses the meanings of a set of reply commands,
turning the lowercase variants, which by default address all recipients
included in the header of a message
.Pf ( Ic reply , respond , followup )
into the uppercase variants, which by default address the sender only
.Pf ( Ic Reply , Respond , Followup )
and vice versa.
The commands
.Ic replysender , respondsender , followupsender
as well as
.Ic replyall , respondall , followupall
are not affected by the current setting of
.Va flipr .
.
.Mx
.It Va followup-to
Controls whether a
.Ql Mail-Followup-To:
header is generated when sending messages to known mailing lists.
Also see
.Va followup-to-honour
and the commands
.Ic mlist , mlsubscribe , reply
and
.Ic Lreply .
.
.Mx
.It Va forward-as-attachment
Original messages are normally sent as inline text with the
.Ic forward
command,
and only the first part of a multipart message is included.
With this option messages are sent as unmodified MIME
.Ql message/rfc822
attachments with all of their parts included.
.
.Mx
.It Va fullnames
When replying to or forwarding a message \*(UA normally removes the
comment and name parts of email addresses.
If this variable is set such stripping is not performed,
and comments, names etc. are retained.
.
.Mx
.It Va header
Causes the header summary to be written at startup and after commands
that affect the number of messages or the order of messages in the
current folder; enabled by default.
The command line option
.Fl N
can be used to set
.Pf no Va header .
.
.Mx
.It Va history-gabby
\*(OP Add more entries to the history as is normally done.
.
.Mx
.It Va history-gabby-persist
\*(OP \*(UAs own NCL will not save the additional (gabby) history
entries in persistent storage unless this variable is also set.
Also see
.Va NAIL_HISTFILE .
.
.Mx
.It Va hold
This option is used to hold messages in the system mailbox by default.
.
.Mx
.It Va idna-disable
\*(OP Can be used to turn off the automatic conversion of domain names
according to the rules of IDNA (internationalized domain names for
applications).
Since the IDNA code assumes that domain names are specified with the
.Va ttycharset
character set, an UTF-8 locale charset is required to represent all
possible international domain names (before conversion, that is).
.
.Mx
.It Va ignore
Ignore interrupt signals from the terminal while entering messages;
instead echo them as
.Ql @
characters and discard the current line.
.
.Mx
.It Va ignoreeof
Ignore end-of-file conditions
.Pf ( Ql control-D ) ,
on message input, which instead can be terminated only by entering a
.Va dot
.Ql \&.
on a line by itself or by using the
.Ic ~.
.Sx "TILDE ESCAPES" .
This option also applies to \*(UA command mode.
.
.Mx Va imap-use-starttls
.It Va imap-use-starttls-USER@HOST , imap-use-starttls-HOST , imap-use-starttls
\*(OP Causes \*(UA to issue a `STARTTLS' command to make an unencrypted
IMAP session SSL/TLS encrypted.
This functionality is not supported by all servers,
and is not used if the session is already encrypted by the IMAPS method.
.
.Mx
.It Va keep
If set, an empty mailbox file is not removed.
This may improve the interoperability with other mail user agents
when using a common folder directory, and prevents malicious users
from creating fake mailboxes in a world-writable spool directory.
Note this only applies to local regular (MBOX) files, other mailbox
types will never be removed.
.
.Mx
.It Va keepsave
When a message is saved it is usually discarded from the originating
folder when \*(UA is quit.
Setting this option causes all saved message to be retained.
.
.Mx
.It Va line-editor-disable
Turn off any enhanced command line editing capabilities (see
.Sx "Command line editor"
for more).
.
.Mx
.It Va markanswered
When a message is replied to and this variable is set,
it is marked as having been answered.
This mark has no technical meaning in the mail system;
it just causes messages to be marked in the header summary,
and makes them specially addressable.
.
.Mx
.It Va message-id-disable
By setting this option the generation of
.Ql Message-ID:
can be completely suppressed, effectively leaving this task up to the
mail-transfer-agent (MTA) or the SMTP server.
(According to RFC 5321 your SMTP server is not required to add this
field by itself, so you should ensure that it accepts messages without a
.Ql Message-ID . )
.
.Mx
.It Va metoo
Usually, when an
.Ic alias
expansion contains the sender, the sender is removed from the expansion.
Setting this option suppresses these removals.
Note that a set
.Va metoo
also causes a
.Ql -m
option to be passed to mail-transfer-agents (MTAs);
though most of the modern MTAs don't (no longer) document this flag, no
MTA is known which doesn't support it (for historical compatibility).
.
.Mx
.It Va mime-allow-text-controls
When sending messages, each part of the message is MIME-inspected in
order to classify the
.Ql Content-Type:
and
.Ql Content-Transfer-Encoding:
(see
.Va encoding )
that is required to send this part over mail transport, i.e.,
a computation rather similar to what the
.Xr file 1
command produces when used with the
.Ql --mime
option.
.Pp
This classification however treats text files which are encoded in
UTF-16 (seen for HTML files) and similar character sets as binary
octet-streams, forcefully changing any
.Ql text/plain
or
.Ql text/html
specification to
.Ql application/octet-stream :
If that actually happens a yet unset charset MIME parameter is set to
.Ql binary ,
effectively making it impossible for the receiving MUA to automatically
interpret the contents of the part.
.Pp
If this option is set, and the data was unambiguously identified as text
data at first glance (by a
.Ql .txt
or
.Ql .html
file extension), then the original
.Ql Content-Type:
will not be overwritten.
.
.Mx Va netrc-lookup
.It Va netrc-lookup-USER@HOST , netrc-lookup-HOST , netrc-lookup
\*(IN \*(OP Used to control usage of the users
.Pa .netrc
file for lookup of account credentials, as documented in the section
.Sx "On URL syntax and credential lookup"
and for the command
.Ic netrc ;
the section
.Sx "The .netrc file"
documents the file format.
.
.Mx
.It Va outfolder
Causes the filename given in the
.Va record
variable
and the sender-based filenames for the
.Ic Copy
and
.Ic Save
commands to be interpreted relative to the directory given in the
.Va folder
variable rather than to the current directory,
unless it is set to an absolute pathname.
.
.Mx
.It Va page
If set, each message the
.Ic pipe
command prints out is followed by a formfeed character
.Ql \ef .
.
.Mx
.It Va piperaw
Send messages to the
.Ic pipe
command without performing MIME and character set conversions.
.
.Mx
.Mx Va pop3-bulk-load
.It Va pop3-bulk-load-USER@HOST , pop3-bulk-load-HOST , pop3-bulk-load
\*(OP When accessing a POP3 server \*(UA loads the headers of the
messages, and only requests the message bodies on user request.
For the POP3 protocol this means that the message headers will be
downloaded twice.
If this option is set then \*(UA will download only complete messages
from the given POP3 server(s) instead.
.
.Mx Va pop3-no-apop
.It Va pop3-no-apop-USER@HOST , pop3-no-apop-HOST , pop3-no-apop
\*(OP Unless this variable is set the
.Ql APOP
authentication method will be used when connecting to a POP3 server that
advertises support.
The advantage of
.Ql APOP
is that the password is not sent in clear text over the wire and that
only a single packet is sent for the user/password tuple.
Note that
.Va pop3-no-apop-HOST
requires \*(IN.
.
.Mx Va pop3-use-starttls
.It Va pop3-use-starttls-USER@HOST , pop3-use-starttls-HOST , pop3-use-starttls
\*(OP Causes \*(UA to issue a
.Ql STLS
command to make an unencrypted POP3 session SSL/TLS encrypted.
This functionality is not supported by all servers,
and is not used if the session is already encrypted by the POP3S method.
Note that
.Va pop3-use-starttls-HOST
requires \*(IN.
.
.Mx
.It Va print-all-chars
This option causes all characters to be considered printable.
It is only effective if given in a startup file.
With this option set some character sequences in messages may put the
user's terminal in an undefined state when printed;
it should only be used as a last resort if no working system locale can
be found.
.
.Mx
.It Va print-alternatives
When a MIME message part of type
.Ql multipart/alternative
is displayed and it contains a subpart of type
.Ql text/plain ,
other parts are normally discarded.
Setting this variable causes all subparts to be displayed,
just as if the surrounding part was of type
.Ql multipart/mixed .
.
.Mx
.It Va quiet
Suppresses the printing of the version when first invoked.
.
.Mx
.It Va quote-as-attachment
If this is set, then the original message is added in its entirety as a
.Ql message/rfc822
MIME attachment when replying to a message.
Note this works regardless of the setting of
.Va quote .
.
.Mx
.It Va recipients-in-cc
On group replies, specify only the sender of the original mail in
.Ql To:
and mention the other recipients in the secondary
.Ql Cc: .
By default all recipients of the original mail will be addressed via
.Ql To: .
.
.Mx
.It Va record-resent
If both this variable and the
.Va record
variable are set,
the
.Ic resend
and
.Ic Resend
commands save messages to the
.Va record
folder as it is normally only done for newly composed messages.
.
.Mx
.It Va reply-in-same-charset
If this variable is set \*(UA first tries to use the same character set
of the original message for replies.
If this fails, the mechanism described in
.Sx "Character sets"
is evaluated as usual.
.
.Mx
.It Va rfc822-body-from_
This variable can be used to force displaying a so-called
.Ql From_
line for messages that are embedded into an envelope mail via the
.Ql message/rfc822
MIME mechanism, for more visual convenience.
.
.Mx
.It Va save
Enable saving of (partial) messages in
.Ev DEAD
upon interrupt or delivery error.
.
.Mx
.It Va searchheaders
Expand message-list specifiers in the form
.Ql /x:y
to all messages containing the substring
.Dq y
in the header field
.Ql x .
The string search is case insensitive.
.
.Mx
.It Va sendcharsets-else-ttycharset
\*(OP If this variable is set, but
.Va sendcharsets
is not, then \*(UA acts as if
.Va sendcharsets
had been set to the value of the variable
.Va ttycharset .
In effect this combination passes through the message data in the
character set of the current locale (given that
.Va ttycharset
hasn't been set manually), i.e., without converting it to the
.Va charset-8bit
fallback character set.
Thus, mail message text will be in ISO-8859-1 encoding when send from
within a ISO-8859-1 locale, and in UTF-8 encoding when send from within
an UTF-8 locale.
If no character set conversion capabilities are available in \*(UA then
the only supported character set is
.Va ttycharset .
.
.It Va sendmail-no-default-arguments
Unless this option is set \*(UA will pass some well known
standard command line options to the defined
.Va sendmail
program, see there for more.
.
.Mx
.It Va sendwait
When sending a message wait until the MTA (including the builtin SMTP
one) exits before accepting further commands.
.Sy Only
with this variable set errors reported by the MTA will be recognizable!
If the MTA returns a non-zero exit status,
the exit status of \*(ua will also be non-zero.
.
.Mx
.It Va showlast
Setting this option causes \*(UA to start at the last message instead of
the first one when opening a mail folder.
.
.Mx
.It Va showname
Causes \*(UA to use the sender's real name instead of the plain address
in the header field summary and in message specifications.
.
.Mx
.It Va showto
Causes the recipient of the message to be shown in the header summary
if the message was sent by the user.
.
.Mx
.It Va skipemptybody
If an outgoing message does not contain any text in its first or only
message part,
do not send it but discard it silently (see also the command line option
.Fl E ) .
.
.Mx
.It Va smime-force-encryption
\*(OP Causes \*(UA to refuse sending unencrypted messages.
.
.Mx
.It Va smime-sign
\*(OP S/MIME sign outgoing messages with the user's private key and
include the user's certificate as a MIME attachment.
Signing a message enables a recipient to verify that the sender used
a valid certificate,
that the email addresses in the certificate match those in the message
header and that the message content has not been altered.
It does not change the message text,
and people will be able to read the message as usual.
Also see
.Va smime-sign-cert , smime-sign-include-certs
and
.Va smime-sign-message-digest .
.
.Mx
.It Va smime-no-default-ca
\*(OP Don't load default CA locations when verifying S/MIME signed
messages.
.
.Mx Va smtp-use-starttls
.It Va smtp-use-starttls-USER@HOST , smtp-use-starttls-HOST , smtp-use-starttls
\*(OP Causes \*(UA to issue a
.Ql STARTTLS
command to make an SMTP session SSL/TLS encrypted, i.e., to enable
transport layer security.
.
.Mx
.It Va ssl-no-default-ca
\*(OP Don't load default CA locations to verify SSL/TLS server
certificates.
.
.Mx
.It Va term-ca-mode
\*(OP If terminal capability queries are supported and this option is
set then \*(UA will try to switch to the
.Dq alternate screen
when in interactive mode, so that the terminal will go back to the
normal screen, leaving all the text there intact, when \*(UA exits.
.Sy Note:
even when supported for this to produce appealing results the used
.Ev PAGER
and possibly configured
.Va pipe-TYPE/SUBTYPE
applications that take control over the terminal need to have
corresponding support too, e.g., the
.Xr less 1
pager should be driven with the
.Ql -X
command line flag.
.
.Mx
.It Va keep-content-length
When (editing messages and) writing
.Ev MBOX
mailbox files \*(UA can be told to keep the
.Ql Content-Length:
and
.Ql Lines:
header fields that some MUAs generate by setting this variable.
Since \*(UA does neither use nor update these non-standardized header
fields (which in itself shows one of their conceptual problems),
stripping them should increase interoperability in between MUAs that
work with with same mailbox files.
Note that, if this is not set but
.Va writebackedited ,
as below, is, a possibly performed automatic stripping of these header
fields already marks the message as being modified.
.
.Mx
.It Va v15-compat
Setting this option enables upward compatibility with \*(UA version 15.0
in respect to which configuration options are available and how they are
handled.
This manual uses \*(IN and \*(OU to refer to the new and the old way of
doing things, respectively.
.
.Mx
.It Va verbose
Setting this option, also controllable via the command line option
.Fl v ,
causes \*(UA to be more verbose, so that, e.g., certificate chains will
be displayed on the users terminal.
Setting this binary option twice increases the level of verbosity, in
which case even details of the actual message delivery and protocol
conversations are shown.
A single
.Pf no Va verbose
is sufficient to disable verbosity as such.
.
.Mx
.It Va writebackedited
If this variable is set messages modified using the
.Ic edit
or
.Ic visual
commands are written back to the current folder when it is quit;
it is only honoured for writable folders in MBOX format, though.
Note that the editor will be pointed to the raw message content in that
case, i.e., neither MIME decoding nor decryption will have been
performed, and proper RFC 4155
.Ql From_
quoting of newly added or edited content is also left as an excercise to
the user.
.El
.\" }}}
.
.\" .Ss "Value options" {{{
.Ss "Value options"
.
Options with values that are generally treated as strings.
To embed whitespace (space and tabulator) in a value it either needs to
be escaped with a backslash character, or the entire value must be
enclosed in (double or single) quotation marks;
To use quotation marks identical to those used to enclose the value,
escape them with a backslash character.
The backslash character has no special meaning except in these cases.
.
.Bd -literal -offset indent
set 1=val\e one 2="val two" 3='val "three"' 4='val \e'four\e''
varshow 1 2 3 4
unset 1 2 3 4
.Ed
.
.Pp
Booleans are special string values that must either be set to decimal
integers (in which case
.Ql 0
is false and
.Ql 1
and any other value is true) or to any of
.Ql off ,
.Ql no
and
.Ql false
for a false boolean and
.Ql on ,
.Ql yes
and
.Ql true
for a true boolean; matching is performed case-insensitively.
And there exists a special kind of boolean, the
.Dq quadoption :
this is expected to either name a boolean or one of the strings
.Ql ask-yes
and
.Ql ask-no
(in fact:
.Ql ask-
followed by a valid boolean, case-insensitively);
if one of the latter is set then in interactive mode the user will be
prompted with the default value (also used for empty user input) set to
the given boolean, whereas in non-interactive the given default will
be used right away.
.
.Bl -tag -width ".It Va _utoprin_"
.Mx Va agent-shell-lookup
.It Va agent-shell-lookup-USER@HOST , agent-shell-lookup-HOST , \
  agent-shell-lookup
\*(IN \*(OP Account passwords can be fetched via an external agent
program in order to permit encrypted password storage \(en see
.Sx "On URL syntax and credential lookup"
for more on credential lookup.
If this is set then the content is interpreted as a shell command the
output of which (with newline characters removed) is treated as the
account password shall the command succeed (and have produced non-empty
non-newline output); e.g., via
.Xr gpg 1 :
.Bd -literal -offset indent
$ echo PASSWORD > .pass
$ gpg -e .pass
$ eval `gpg-agent --daemon \e
    --pinentry-program=/usr/bin/pinentry-curses \e
    --max-cache-ttl 99999 --default-cache-ttl 99999`
$ echo 'set agent-shell-lookup="gpg -d .pass.gpg"' \e
    >> \*(ur
.Ed
.Pp
A couple of environment variables will be set for the agent:
.Pp
.Bl -tag -compact -width ".It Ev _AIL_TMPDIR[337]"
.It Ev NAIL_TMPDIR
The temporary directory that \*(UA uses.
Usually identical to
.Ev TMPDIR ,
but guaranteed to be set and usable by child processes;
to ensure the latter condition for
.Ev TMPDIR
also, it'll be set.
.It Ev NAIL_USER
The user
.Pf ( Ql USER )
for which the password is looked up.
.It Ev NAIL_USER_ENC
The URL percent-encoded variant of
.Ev NAIL_USER .
.It Ev NAIL_HOST
The plain machine hostname of the user account.
.It Ev NAIL_HOST_PORT
The
.Ql HOST
(hostname possibly including port) of the user account.
.El
.
.Mx
.It Va attrlist
A sequence of characters to print in the
.Ql attribute
column of the
.Va headline
as shown in the header display; each for one type of messages (see
.Sx "Message states" ) ,
with the default being
.Ql NUROSPMFAT+\-$~
or
.Ql NU\ \ *HMFAT+\-$~
if
.Va bsdflags
or the
.Ev SYSV3
environment variable are set, in the following order:
.Pp
.Bl -tag -compact -offset indent -width ".It Ql _"
.It Ql N
new.
.It Ql U
unread but old.
.It Ql R
new but read.
.It Ql O
read and old.
.It Ql S
saved.
.It Ql P
preserved.
.It Ql M
mboxed.
.It Ql F
flagged.
.It Ql A
answered.
.It Ql T
draft.
.It Ql +
start of a collapsed thread.
.It Ql -
collapsed.
.It Ql $
classified as spam.
.It Ql ~
classified as possible spam.
.El
.
.Mx
.It Va autobcc
Specifies a list of recipients to which a blind carbon copy of each
outgoing message will be sent automatically.
.
.Mx
.It Va autocc
Specifies a list of recipients to which a carbon copy of each outgoing
message will be sent automatically.
.
.Mx
.It Va autosort
Causes sorted mode (see the
.Ic sort
command) to be entered automatically with the value of this option as
sorting method when a folder is opened.
.
.Mx
.It Va charset-7bit
The value that should appear in the
.Ql charset=
parameter of
.Ql Content-Type:
MIME header fields when no character set conversion of the message data
was performed.
This defaults to US-ASCII, and the chosen character set should be
US-ASCII compatible.
.
.Mx
.It Va charset-8bit
\*(OP The default 8-bit character set that is used as an implicit last
member of the variable
.Va sendcharsets .
This defaults to UTF-8.
If no character set conversion capabilities are available in \*(UA then
the only supported character set is
.Va ttycharset .
Refer to the section
.Sx "Character sets"
for the complete picture of character set conversion in \*(UA.
.
.Mx
.It Va charset-unknown-8bit
\*(OP RFC 1428 specifies conditions when internet mail gateways shall
.Dq upgrade
the content of a mail message by using a character set with the name
.Ql unknown-8bit .
Because of the unclassified nature of this character set \*(UA will not
be capable to convert this character set to any other character set.
If this variable is set any message part which uses the character set
.Ql unknown-8bit
is assumed to really be in the character set given in the value,
otherwise the (final) value of
.Va charset-8bit
is used for this purpose.
.
.Mx
.It Va cmd
The default value for the
.Ic pipe
command.
.
.Mx
.It Va colour-from_
\*(OP The colour specification for so-called
.Ql From_
lines.
See the section
.Sx "Coloured message display"
for the format of the value.
.
.Mx
.It Va colour-header
\*(OP The colour specification for header lines.
.
.Mx
.It Va colour-msginfo
\*(OP The colour specification for the introductional message info line.
.
.Mx
.It Va colour-partinfo
\*(OP The colour specification for MIME part info lines.
.
.Mx
.It Va colour-terms
\*(OP A comma-separated list of
.Ev TERM Ns
inals for which coloured message display can be used.
Entries only need to be added if the string
.Dq color
isn't part of the terminal name itself; the default value is
.Pp
.Dl cons25,linux,rxvt,rxvt-unicode,\:screen,\:sun,\:vt100,\:vt220,\:\
wsvt25,\:xterm
.
.Mx
.It Va colour-uheader
\*(OP The colour specification for those header lines that have been
placed in the
.Va colour-user-headers
list.
See the section
.Sx "Coloured message display" .
.
.Mx
.It Va colour-user-headers
A comma separated list of (case-insensitive) header names which should
be colourized with the alternative
.Va colour-uheader
colours.
The default value is
.Ql from,subject .
.
.Mx
.It Va crt
In a(n interactive) terminal session, then if this valued option is set
it'll be used as a threshold to determine how many lines the given
output has to span before it will be displayed via the configured
.Ev PAGER ;
Usage of the
.Ev PAGER
can be forced by setting this to the value
.Ql 0 ,
setting it without a value will deduce the current height of the
terminal screen to compute the treshold (see
.Ev LINES
and
.Xr stty 1 ) .
.
.Mx
.It Va datefield
The date in a header summary is normally the date of the mailbox
.Ql From_
line of the message.
If this variable is set, then the date as given in the
.Ql Date:
field is used, converted to local time.
It is possible to control the display of the date by assigning a value,
in which case the
.Xr strftime 3
function will be used to format the date accordingly.
Please read your system manual for the available formats.
Note that the
.Ql %n
format should not be used, because \*(UA doesn't take embedded newlines
into account when calculating how many lines fit onto the screen.
.
.Mx
.It Va datefield-markout-older
This option, when set in addition to
.Va datefield ,
is used to display
.Dq older
messages (concept is rather comparable to the
.Fl \&\&l
option of the POSIX utility
.Xr ls 1 ) .
The content interpretation is identical to
.Va datefield .
.
.Mx
.It Va encoding
Suggestion for the MIME encoding to use in outgoing text messages
and message parts.
Valid values are the default
.Ql quoted-printable ,
.Ql 8bit
and
.Ql base64 .
.Ql 8bit
may cause problems when transferring mail messages over channels that
are not ESMTP (RFC 1869) compliant.
If there is no need to encode a message,
.Ql 7bit
transfer mode is always used regardless of this variable.
Binary data is always encoded as
.Ql base64 .
.
.Mx
.It Va escape
If defined, the first character of this option
gives the character to use in place of
.Ql ~
to denote
.Sx "TILDE ESCAPES" .
.
.Mx
.It Va expandaddr
If not set then file and command pipeline targets are not allowed,
and any such address will be filtered out, giving a warning message.
If set without a value then all possible recipient address
specifications will be accepted \(en see the section
.Sx "Sending mail"
for more on this.
To accept them, but only in interactive mode, or when tilde commands
were enabled explicitly by using one of the command line options
.Fl ~
or
.Fl # ,
set this to the (case-insensitive) value
.Ql restrict
(note right now this is actually like setting
.Ql restrict,-all,+name,+addr ) .
.Pp
In fact the value is interpreted as a comma-separated list of values.
If it contains
.Ql fail
then the existence of disallowed specifications is treated as a hard
send error instead of only filtering them out.
The remaining values specify whether a specific type of recipient
address specification is allowed (optionally indicated by a plus sign
.Ql +
prefix) or disallowed (prefixed with a hyphen
.Ql - ) .
The value
.Ql all
addresses all possible address specifications,
.Ql file
file targets,
.Ql pipe
command pipeline targets,
.Ql name
plain user names and (MTA) aliases (\*(OB
.Ql noalias
may be used as an alternative syntax to
.Ql -name )
and
.Ql addr
network addresses.
These kind of values are interpreted in the given order, so that
.Ql restrict,\:fail,\:+file,\:-all,\:+addr
will cause hard errors for any non-network address recipient address
unless \*(UA is in interactive mode or has been started with the
.Fl ~
or
.Fl #
command line option; in the latter case(s) any address may be used, then.
.
.Mx
.It Va expandargv
Unless this variable is set additional mail-transfer-agent (MTA)
arguments from the command line, as can be given after a
.Ql --
separator, are ignored due to safety reasons.
However, if set to the special value
.Ql fail ,
then the presence of additional MTA arguments is treated as a hard
error that causes \*(UA to exit with failure status.
A lesser strict variant is the otherwise identical
.Ql restrict ,
which does accept such arguments in interactive mode, or if tilde
commands were enabled explicitly by using one of the command line options
.Fl ~
or
.Fl # .
.
.Mx
.It Va features
\*(RO Information on the features compiled into \*(UA \(en the content
of this variable is identical to the output of the command
.Ic features .
.
.Mx
.Mx
.It Va file-hook-load-EXTENSION , file-hook-save-EXTENSION
It is possible to install file hooks which will be used by the
.Ic file
command in order to be able to transparently handle (through an
intermediate temporary file) files with specific
.Ql EXTENSION Ns
s: the variable values can include shell snippets and are expected to
write data to standard output / read data from standard input,
respectively.
\*(ID The variables may not be changed while there is a mailbox
attendant.
.Bd -literal -offset indent
set file-hook-load-xy='echo >&2 XY-LOAD; gzip -cd' \e
    file-hook-save-xy='echo >&2 XY-SAVE; gzip -c' \e
    record=+null-sent.xy
.Ed
.
.Mx
.It Va folder
The name of the directory to use for storing folders of messages.
All folder names that begin with
.Ql +
refer to files below it.
The same special conventions as documented for the
.Ic file
command may be used when specifying a new value for
.Va \&\&folder ,
but be aware that the expansion is fully performed immediately.
E.g., if the expanded name refers to an IMAP account, all names that
begin with `+' refer to IMAP mailboxes below the
.Va folder
target box.
.Pp
Note: for IMAP it makes a difference whether
.Va \&\&folder
ends with a directory separator solidus or not in respect to the
automatic append of `INBOX' strings.
Ssome IMAP servers do not accept the creation of mailboxes in
the hierarchy base, but require that they are created as subfolders of
`INBOX' \(en with such servers a folder name of the form
.Pp
.Dl imaps://mylogin@imap.myisp.example/INBOX.
.Pp
should be used (the last character is the server's hierarchy delimiter).
Folder names prefixed by `+' will then refer to folders below `INBOX',
while folder names prefixed by `@' refer to folders below the hierarchy
base.
See the
.Ic imap
namespace command for a method to detect the appropriate prefix and
delimiter.
.
.Mx
.It Va folder-hook
When a folder is opened and this variable is set,
the macro corresponding to the value of this variable is executed.
The macro is also invoked when new mail arrives,
but message lists for commands executed from the macro
only include newly arrived messages then.
If
.Ic localopts
are activated in a folder hook, then the covered settings will be
reverted once the folder is left again.
.
.Mx
.It Va folder-hook-FOLDER
Overrides
.Va folder-hook
for a folder named
.Ql FOLDER .
Unlike other folder specifications, the fully expanded name of a folder,
without metacharacters, is used to avoid ambiguities.
However, if the mailbox resides under
.Va folder
then the usual
.Ql +
specification is tried in addition, e.g., if
.Va \&\&folder
is
.Dq mail
(and thus relative to the user's home directory) then
.Pa /home/usr1/mail/sent
will be tried as
.Ql folder-hook-/home/usr1/mail/sent
first, but then followed by
.Ql folder-hook-+sent .
.
.Mx
.It Va followup-to-honour
Controls whether a
.Ql Mail-Followup-To:
header is honoured when group-replying to a message via
.Ic reply
or
.Ic Lreply .
This is a quadoption; if set without a value it defaults to
.Dq yes .
Also see
.Va followup-to
and the commands
.Ic mlist
and
.Ic mlsubscribe .
.
.Mx
.It Va from
The address (or a list of addresses) to put into the
.Ql From:
field of the message header, quoting RFC 5322:
the author(s) of the message, that is, the mailbox(es) of the person(s)
or system(s) responsible for the writing of the message.
If replying to messages these addresses are handled as if they were in
the
.Ic alternates
list.
If the machine's hostname is not valid at the Internet (for example at
a dialup machine) then either this variable or
.Va hostname
(\*(IN and with
.Va smtp
.Va smtp-hostname
adds even more fine-tuning capabilities),
have to be set.
If
.Va \&\&from
contains more than one address,
setting the
.Va sender
variable is required (according to the standard RFC 5322).
.
.Mx
.It Va fwdheading
The string to print before the text of a message with the
.Ic forward
command
(unless the
.Va forward-as-attachment
variable is set).
Defaults to
.Dq -------- Original Message --------
if unset; No heading is printed if it is set to the empty string.
.
.Mx
.It Va headline
A format string to use for the header summary,
similar to
.Xr printf 3
formats.
A percent character
.Ql %
introduces a format specifier that may be followed by a number
indicating the field width;
If the (possibly implicitly implied) field width is negative, the field
is to be left-aligned.
Valid format specifiers are:
.Pp
.Bl -tag -compact -offset indent -width "_%%_"
.It Ql %%
A plain percent character.
.It Ql %>
A space character but for the current message, for which it expands to
.Ql > .
.It Ql %<
A space character but for the current message, for which it expands to
.Ql < .
.It Ql %$
\*(OP The spam score of the message, as has been classified via the
command
.Ic spamrate .
Prints only a replacement character if there is no spam support.
.It Ql %a
Message attribute character (status flag); the actual content can be
adjusted by setting
.Va attrlist .
.It Ql %d
The date when the message was received.
.It Ql %e
The indenting level in threaded mode.
.It Ql %f
The address of the message sender.
.It Ql %i
The message thread structure.
(Note that this format doesn't support a field width.)
.It Ql %l
The number of lines of the message.
.It Ql %m
Message number.
.It Ql %o
The number of octets (bytes) in the message.
.It Ql %s
Message subject (if any).
.It Ql %S
Message subject (if any) in double quotes.
.It Ql \&%T
Message recipient flags: is the addressee of the message a known or
subscribed mailing list \(en see
.Ic mlist
and
.Ic mlsubscribe .
.It Ql %t
The position in threaded/sorted order.
.El
.Pp
The default is
.Ql %>\&%a\&%m\ %-18f\ %16d\ %4l/%\-5o\ %i%-s ,
or
.Ql %>\&%a\&%m\ %20-f\ \ %16d\ %3l/%\-5o\ %i%-S
if
.Va bsdcompat
is set.
Also see
.Va attrlist
and
.Va headline-bidi .
.
.Mx
.It Va headline-bidi
Bidirectional text requires special treatment when displaying headers,
because numbers (in dates or for file sizes etc.) will not affect the
current text direction, in effect resulting in ugly line layouts when
arabic or other right-to-left text is to be displayed.
On the other hand only a minority of terminals is capable to correctly
handle direction changes, so that user interaction is necessary for
acceptable results.
Note that extended host system support is required nonetheless, e.g.,
detection of the terminal character set is one precondition;
and this feature only works in an Unicode (i.e., UTF-8) locale.
.Pp
In general setting this variable will cause \*(UA to encapsulate text
fields that may occur when printing
.Va headline
(and some other fields, like dynamic expansions in
.Va prompt )
with special Unicode control sequences;
it is possible to fine-tune the terminal support level by assigning
a value:
no value (or any value other than
.Ql 1 ,
.Ql 2
and
.Ql 3 )
will make \*(UA assume that the terminal is capable to properly deal
with Unicode version 6.3, in which case text is embedded in a pair of
U+2068 (FIRST STRONG ISOLATE) and U+2069 (POP DIRECTIONAL ISOLATE)
characters.
In addition no space on the line is reserved for these characters.
.Pp
Weaker support is chosen by using the value
.Ql 1
(Unicode 6.3, but reserve the room of two spaces for writing the control
sequences onto the line).
The values
.Ql 2
and
.Ql 3
select Unicode 1.1 support (U+200E, LEFT-TO-RIGHT MARK); the latter
again reserves room for two spaces in addition.
.
.Mx
.It Va hostname
Use this string as hostname when expanding local addresses instead of
the value obtained from
.Xr uname 3
and
.Xr getaddrinfo 3 ,
i.e., in
.Ql Message-ID:
and
.Ql From:
fields.
Note that when
.Va smtp
transport is not used then it is normally the responsibility of the MTA
to create these fields, \*(IN in conjunction with
.Va smtp
however
.Va smtp-hostname
also influences the results;
you should produce some test messages with the desired combination of
.Va \&\&hostname ,
and/or
.Va from ,
.Va sender
etc. first.
.
.Mx Va imap-auth
.It Va imap-auth-USER@HOST , imap-auth
\*(OP Sets the IMAP authentication method.
Valid values are `login' for the usual password-based authentication
(the default),
`cram-md5', which is a password-based authentication that does not send
the password over the network in clear text,
and `gssapi' for GSS-API based authentication.
.
.Mx
.It Va imap-cache
\*(OP Enables caching of IMAP mailboxes.
The value of this variable must point to a directory that is either
existent or can be created by \*(UA.
All contents of the cache can be deleted by \*(UA at any time;
it is not safe to make assumptions about them.
.
.Mx Va imap-delim
.It Va imap-delim-USER@HOST , imap-delim-HOST , imap-delim
\*(OP The hierarchy separator used by the IMAP server.
Whenever an IMAP path is specified it will undergo normalization.
One of the normalization steps is the squeeze and adjustment of
hierarchy separators.
If this variable is set, any occurrence of any character of the given
value that exists in the path will be replaced by the first member of
the value; an empty value will cause the default to be used, it is
.Ql /. .
If not set, we will reuse the first hierarchy separator character that
is discovered in a user-given mailbox name.
.
.Mx Va imap-keepalive
.It Va imap-keepalive-USER@HOST , imap-keepalive-HOST , imap-keepalive
\*(OP IMAP servers may close the connection after a period of
inactivity; the standard requires this to be at least 30 minutes,
but practical experience may vary.
Setting this variable to a numeric `value' greater than 0 causes
a `NOOP' command to be sent each `value' seconds if no other operation
is performed.
.
.Mx
.It Va imap-list-depth
\*(OP When retrieving the list of folders on an IMAP server, the
.Ic folders
command stops after it has reached a certain depth to avoid possible
infinite loops.
The value of this variable sets the maximum depth allowed.
The default is 2.
If the folder separator on the current IMAP server is a slash `/',
this variable has no effect and the
.Ic folders
command does not descend to subfolders.
.
.Mx
.It Va inbox
If this is set it will be used for expansions of
.Ql % ,
see
.Ic file
for more.
\*(ID IMAP users may set this to the empty string to force bypassing the
special handling of
.Va folder .
The value supports a subset of filename expansions itself.
.
.Mx
.It Va indentprefix
String used by the
.Ic ~m , ~M
and
.Ic ~R
.Sx "TILDE ESCAPES"
and by the
.Va quote
option for indenting messages,
in place of the normal tabulator character
.Ql ^I ,
which is the default.
Be sure to quote the value if it contains spaces or tabs.
.
.Mx
.It Va line-editor-cursor-right
\*(OP If the builtin command line editor is used, actions which are
based on rightwise movement may not work on some terminals.
If you encounter such problems, set this variable to the terminal
control sequence that is necessary to move the cursor one column to the
right.
The default is
.Ql \e033[C ,
which should work for most terminals.
Less often occur
.Ql \e033OC
and
.Ql \e014 .
Note that
.Dq Escape
and other control character have to be written as shell-style escape
sequences, e.g.,
.Ql \e033
for (US-ASCII)
.Dq Escape .
.
.Mx
.It Va MAIL
Is used as the user's mailbox, if set.
Otherwise, a system-dependent default is used.
Supports a logical subset of the special conventions that are documented
for the
.Ic file
command and the
.Va folder
option.
.
.Mx
.It Va mime-counter-evidence
Normally the
.Ql Content-Type:
field is used to decide how to handle MIME parts.
Some MUAs however don't use
.Xr mime.types 5
or a similar mechanism to correctly classify content, but simply specify
.Ql application/octet-stream ,
even for plain text attachments like
.Ql text/diff .
If this variable is set then \*(UA will try to classify such MIME
message parts on its own, if possible, and through their file name.
This variable can also be given a non-empty value, in which case the
value is expected to be a number, actually a carrier of bits.
Creating the bit-carrying number is a simple addition:
.Bd -literal -offset indent
? !echo Value should be set to $((2 + 4))
Value should be set to 6
.Ed
.Pp
.Bl -bullet -compact
.It
If bit two is set (2) then the detected
.Qd real
content-type will be carried along with the message and be used for
deciding which
.Va pipe-TYPE/SUBTYPE
is responsible for the MIME part, shall that question arise;
when displaying such a MIME part the part-info will indicate the
overridden content-type by showing a plus-sign
.Ql + .
.It
If bit three is set (4) then the counter-evidence is always produced
and a positive result will be used as the MIME type, even forcefully
overriding the parts given MIME type.
.\".It
.\"If bit four is set (8) then as a last resort the content of
.\".Ql application/octet-stream
.\"parts will be inspected, so that data that looks like (english) plain
.\"text can be treated as such.
.El
.
.Mx
.It Va mimetypes-load-control
This option can be used to control which of the
.Xr mime.types 5
databases are loaded by \*(UA, as furtherly described in the section
.Sx "The mime.types files" .
If the letter
.Ql u
is part of the option value, then the user's personal
.Pa ~/.mime.types
file will be loaded (if it exists); likewise the letter
.Ql s
controls loading of the system wide
.Pa /etc/mime.types ;
the user file is loaded first, letter matching is case-insensitive.
If this option is not set \*(UA will try to load both files instead.
Incorporation of the \*(UA-builtin MIME types cannot be suppressed,
but they will be matched last.
.Pp
More sources can be specified by using a different syntax: if the
value string contains an equals sign
.Ql =
then it is instead parsed as a comma-separated list of the described
letters plus
.Ql f=FILENAME
pairs; the given filenames will be expanded and loaded, and their
content may use the extended syntax that is described in the section
.Sx "The mime.types files" .
.
.Mx
.It Va NAIL_EXTRA_RC
The name of an optional startup file to be read after
.Pa \*(ur .
This variable has an effect only if it is set in
.Pa \*(UR
or
.Pa \&\&\*(ur ,
it is not imported from the environment in order to honour
.Ql MAILRC=/dev/null Ns /
.Fl n
invocations.
Use this file for commands that are not understood by other POSIX
.Xr mailx 1
implementations.
.
.Mx
.It Va NAIL_HEAD
A string to put at the beginning of each new message.
The escape sequences tabulator
.Ql \et
and newline
.Ql \en
are understood.
.
.Mx
.It Va NAIL_HISTFILE
\*(OP If a command line editor is available then this can be set to
name the (expandable) path of the location of a permanent history file.
.
.Mx
.It Va NAIL_HISTSIZE
\*(OP If a command line editor is available this value restricts the
amount of history entries that are saved into a set and valid
.Va NAIL_HISTFILE .
A value of less than 0 disables this feature;
note that loading and incorporation of
.Va NAIL_HISTFILE
upon program startup can also be suppressed by doing this.
An unset or invalid value, or 0, causes a default value to be used.
Dependent on the available command line editor this will also define the
number of history entries in memory;
it is also editor-specific whether runtime updates of this value will be
honoured.
.
.Mx
.It Va NAIL_TAIL
A string to put at the end of each new message.
The escape sequences tabulator
.Ql \et
and newline
.Ql \en
are understood.
.
.Mx
.It Va newfolders
If this variable has the value
.Ql maildir ,
newly created local folders will be in Maildir format.
.
.Mx
.It Va newmail
Checks for new mail in the current folder each time the prompt is
printed.
For IMAP mailboxes the server is then polled for new mail,
which may result in delayed operation if the connection to the server is
slow.
A Maildir folder must be re-scanned to determine if new mail has arrived.
.Pp
If this variable is set to the special value
.Dq nopoll
an IMAP server is not actively asked for new mail, but new mail may
still be detected and announced with any other IMAP command that is sent
to the server.
In either case the IMAP server may send notifications about messages
that have been deleted on the server by another process or client.
In this case,
.Dq Expunged X messages
is printed regardless of this variable, and message numbers may have
changed.
.Pp
If this variable is set to the special value
.Ql nopoll
then a Maildir folder will not be rescanned completely, but only
timestamp changes are detected.
.
.Mx
.It Va ORGANIZATION
The value to put into the
.Ql Organization:
field of the message header.
.
.Mx Va password
.It Va password-USER@HOST , password-HOST , password
\*(IN Variable chain that sets a password, which is used in case none has
been given in the protocol and account-specific URL;
as a last resort \*(UA will ask for a password on the user's terminal if
the authentication method requires a password.
Specifying passwords in a startup file is generally a security risk;
the file should be readable by the invoking user only.
.
.It Va password-USER@HOST
\*(OU (see the chain above for \*(IN)
Set the password for
.Ql USER
when connecting to
.Ql HOST .
If no such variable is defined for a host,
the user will be asked for a password on standard input.
Specifying passwords in a startup file is generally a security risk;
the file should be readable by the invoking user only.
.
.Mx
.It Va pipe-TYPE/SUBTYPE
When a MIME message part of type
.Ql TYPE/SUBTYPE
(normalized to lowercase) is displayed or quoted,
its text is filtered through the value of this variable interpreted as
a shell command.
The special value
.Ql @
can be used to force interpretation of the message part as plain text, e.g.,
.Ql set pipe-application/pgp-signature=@
will henceforth treat signatures as plain text and display them "as is".
(The same can also be achieved, in a more useful context, by using the
.Ic mimetype
command in conjunction with a type marker.)
.Pp
Also, if a shell command is prefixed with
.Ql @ ,
then the command will only be used to prepare the MIME message part if
the message is displayed by itself, but not when multiple messages are
displayed at once.
.Pp
Finally, if a shell command is prefixed with
.Ql @& ,
then, in addition to what has been described for the plain
.Ql @
shell command prefix, the command will be run asynchronously, i.e.,
without blocking \*(UA, which may be a handy way to display a, e.g., PDF
file while also continuing to read the mail message.
Some information about the MIME part to be displayed is embedded into
the environment of the shell command:
.Pp
.Bl -tag -compact -width ".It Ev _AIL__ILENAME__ENERATED"
.Mx
.It Ev NAIL_TMPDIR
The temporary directory that \*(UA uses.
Usually identical to
.Ev TMPDIR ,
but guaranteed to be set and usable by child processes;
to ensure the latter condition for
.Ev \&\&TMPDIR
also, it'll be set.
.Mx
.It Ev NAIL_FILENAME
The filename, if any is set, the empty string otherwise.
.Mx
.It Ev NAIL_FILENAME_GENERATED
A random string.
.Mx
.It Ev NAIL_CONTENT
The MIME content-type of the part, if known, the empty string otherwise.
.Mx
.It Ev NAIL_CONTENT_EVIDENCE
If
.Va mime-counter-evidence
includes the carry-around-bit (2), then this will be set to the detected
MIME content-type; not only then identical to
.Ev \&\&NAIL_CONTENT
otherwise.
.El
.
.Mx
.It Va pipe-EXTENSION
This is identical to
.Va pipe-TYPE/SUBTYPE
except that
.Ql EXTENSION
(normalized to lowercase using character mappings of the ASCII charset)
names a file extension, e.g.,
.Ql xhtml .
Handlers registered using this method take precedence.
.
.Mx Va pop3-keepalive
.It Va pop3-keepalive-USER@HOST , pop3-keepalive-HOST , pop3-keepalive
\*(OP POP3 servers close the connection after a period of inactivity;
the standard requires this to be at least 10 minutes,
but practical experience may vary.
Setting this variable to a numeric value greater than
.Ql 0
causes a
.Ql NOOP
command to be sent each value seconds if no other operation is performed.
.
.Mx
.It Va prompt
The string printed when a command is accepted.
Prompting may be prevented by either setting this to the null string
or by setting
.Pf no Va prompt .
The same XSI escape sequences that are understood by the
.Ic echo
command may be used within
.Va \&\&prompt .
.Pp
In addition, the following \*(UA specific additional sequences are
understood:
.Ql \e& ,
which expands to
.Dq \&?
unless
.Va bsdcompat
is set, in which case it expands to
.Dq \&& ;
note that
.Ql \e&\0
is the default value of
.Va \&\&prompt .
.Ql \e? ,
which will expand to
.Dq 1
if the last command failed and to
.Dq 0
otherwise,
.Ql \e$ ,
which will expand to the name of the currently active
.Ic account ,
if any, and to the empty string otherwise, and
.Ql \e@ ,
which will expand to the name of the currently active mailbox.
(Note that the prompt buffer is size-limited, excess is cut off.)
.Pp
Even though
.Va \&\&prompt
checks for
.Va headline-bidi
to encapsulate the expansions of the
.Ql \e$
and
.Ql \e@
escape sequences as necessary to correctly display bidirectional text,
this is not true for the final string that makes up
.Va \&\&prompt
as such, i.e., real BIDI handling is not supported.
.Pp
When a newer version of the
.Xr editline 3
.Sx "Command line editor"
is used, any escape sequence must itself be encapsulated with another
escape character for usage with the
.Va EL_PROMPT_ESC
mechanism: \*(UA configures the control character
.Ql \e01
for this.
.
.Mx
.It Va quote
If set, \*(UA starts a replying message with the original message
prefixed by the value of the variable
.Va indentprefix .
Normally, a heading consisting of
.Dq Fromheaderfield wrote:
is printed before the quotation.
If the string
.Ql noheading
is assigned to the
.Va \&\&quote
variable, this heading is omitted.
If the string
.Ql headers
is assigned, the headers selected by the
.Ic ignore Ns / Ns Ic retain
commands are printed above the message body,
thus
.Va \&\&quote
acts like an automatic
.Pf ` Ic ~m Ns '
.Sx "TILDE ESCAPES"
command, then.
If the string
.Ql allheaders
is assigned, all headers are printed above the message body and all MIME
parts are included, making
.Va \&\&quote
act like an automatic
.Pf ` Ic ~M Ns '
command; also see
.Va quote-as-attachment .
.
.Mx
.It Va quote-fold
\*(OP Can be set in addition to
.Va indentprefix .
Setting this turns on a more fancy quotation algorithm in that leading
quotation characters are compressed and overlong lines are folded.
.Va \&\&quote-fold
can be set to either one or two (space separated) numeric values,
which are interpreted as the maximum (goal) and the minimum line length,
respectively, in a spirit rather equal to the
.Xr fmt 1
program, but line-, not paragraph-based.
If not set explicitly the minimum will reflect the goal algorithmically.
The goal can't be smaller than the length of
.Va indentprefix
plus some additional pad.
Necessary adjustments take place silently.
.
.Mx
.It Va record
If defined, gives the pathname of the folder used to record all outgoing
mail.
If not defined, then outgoing mail is not saved.
When saving to this folder fails the message is not sent,
but instead saved to
.Ev DEAD .
.
.Mx
.It Va reply_strings
Can be set to a comma-separated list of (case-insensitive according to
ASCII rules) strings which shall be recognized in addition to the
builtin strings as
.Ql Subject:
reply message indicators \(en builtin are
.Ql Re: ,
which is mandated by RFC 5322, as well as the german
.Ql Aw: .
.
.Mx
.It Va replyto
A list of addresses to put into the
.Ql Reply-To:
field of the message header.
Members of this list are handled as if they were in the
.Ic alternates
list.
.
.Mx
.It Va reply-to-honour
Controls whether a
.Ql Reply-To:
header is honoured when replying to a message via
.Ic reply
or
.Ic Lreply .
This is a quadoption; if set without a value it defaults to
.Dq yes .
.
.Mx
.It Va screen
When \*(UA initially prints the message headers it determines the number
to print by looking at the speed of the terminal.
The faster the terminal, the more it prints.
This option overrides this calculation and specifies how many message
headers are printed.
This number is also used for scrolling with the
.Ic z
command.
.
.Mx
.It Va sendcharsets
\*(OP A comma-separated list of character set names that can be used in
outgoing internet mail.
The value of the variable
.Va charset-8bit
is automatically appended to this list of character-sets.
If no character set conversion capabilities are compiled into \*(UA then
the only supported charset is
.Va ttycharset .
Also see
.Va sendcharsets-else-ttycharset
and refer to the section
.Sx "Character sets"
for the complete picture of character set conversion in \*(UA.
.
.Mx
.It Va sender
An address that is put into the
.Ql Sender:
field of outgoing messages, quoting RFC 5322: the mailbox of the agent
responsible for the actual transmission of the message.
This field should normally not be used unless the
.Ql From:
field contains more than one address, on which case it is required.
The
.Va \&\&sender
address is handled as if it were in the
.Ic alternates
list.
.
.Mx
.It Va sendmail
To use an alternate mail transport agent (MTA),
set this option to the full pathname of the program to use.
It may be necessary to set
.Va sendmail-progname
in addition.
.Pp
The MTA will be passed command line arguments from several possible
sources: from the variable
.Va sendmail-arguments
if set, from the command line if given and the variable
.Va expandargv
allows their use.
Argument processing of the MTA will be terminated with a
.Ql --
separator.
.Pp
The otherwise occurring implicit usage of the following MTA command line
arguments can be disabled by setting the boolean option
.Va sendmail-no-default-arguments
(which will also disable passing
.Ql --
to the MTA):
.Ql -i
(for not treating a line with only a dot
.Ql \&.
character as the end of input),
.Ql -m
(shall the option
.Va metoo
be set) and
.Ql -v
(if the
.Va verbose
option is set); in conjunction with the
.Fl r
command line option \*(UA will also pass
.Ql -f
as well as
.Ql -F .
.
.Mx
.It Va sendmail-arguments
Arguments to pass through to the Mail-Transfer-Agent can be given via
this option.
The content of this variable will be split up in a vector of arguments
which will be joined onto other possible MTA options:
.Pp
.Dl set sendmail-arguments='-t -X \&"/tmp/my log\&"'
.
.Mx
.It Va sendmail-no-default-arguments
\*(BY Unless this option is set \*(UA will pass some well known
standard command line options to the defined
.Va sendmail
program, see there for more.
.
.Mx
.It Va sendmail-progname
Many systems use a so-called
.Xr mailwrapper 8
environment to ensure compatibility with
.Xr sendmail 1 .
This works by inspecting the name that was used to invoke the mail
delivery system.
If this variable is set then the mailwrapper (the program that is
actually executed when calling
.Dq sendmail )
will treat its contents as that name.
The default is
.Ql sendmail .
.
.Mx
.It Va Sign
A string for use with the
.Ic ~A
tilde escape.
.
.Mx
.It Va sign
A string for use with the
.Ic ~a
tilde escape.
.
.Mx
.It Va signature
Must correspond to the name of a readable file if set.
The file's content is then appended to each singlepart message
and to the first part of each multipart message.
Be warned that there is no possibility to edit the signature for an
individual message.
.
.Mx
.It Va smime-ca-dir
\*(OP Specifies a directory with CA certificates in PEM (Privacy
Enhanced Mail) format for verification of S/MIME signed messages.
.
.Mx
.It Va smime-ca-file
\*(OP Specifies a file with CA certificates in PEM format for
verification of S/MIME signed messages.
.
.Mx Va smime-cipher
.It Va smime-cipher-USER@HOST , smime-cipher
\*(OP Specifies the cipher to use when generating S/MIME encrypted
messages (for the specified account).
RFC 5751 mandates a default of
.Ql aes128
(AES-128 CBC).
Possible values are (case-insensitive and) in decreasing cipher strength:
.Ql aes256
(AES-256 CBC),
.Ql aes192
(AES-192 CBC),
.Ql aes128
(AES-128 CBC),
.Ql des3
(DES EDE3 CBC, 168 bits; default if
.Ql aes128
isn't available) and
.Ql des
(DES CBC, 56 bits).
.Pp
The actually available cipher algorithms depend on the cryptographic
library that \*(UA uses.
\*(OP Support for more cipher algorithms may be available through
dynamic loading via, e.g.,
.Xr EVP_get_cipherbyname 3
(OpenSSL) if \*(UA has been compiled to support this.
.
.Mx
.It Va smime-crl-dir
\*(OP Specifies a directory that contains files with CRLs in PEM format
to use when verifying S/MIME messages.
.
.Mx
.It Va smime-crl-file
\*(OP Specifies a file that contains a CRL in PEM format to use when
verifying S/MIME messages.
.
.Mx
.It Va smime-encrypt-USER@HOST
\*(OP If this variable is set, messages send to the given receiver are
encrypted before sending.
The value of the variable must be set to the name of a file that
contains a certificate in PEM format.
.Pp
If a message is sent to multiple recipients,
each of them for whom a corresponding variable is set will receive an
individually encrypted message;
other recipients will continue to receive the message in plain text
unless the
.Va smime-force-encryption
variable is set.
It is recommended to sign encrypted messages, i.e., to also set the
.Va smime-sign
variable.
.
.Mx Va smime-sign-cert
.It Va smime-sign-cert-USER@HOST , smime-sign-cert
\*(OP Points to a file in PEM format.
For the purpose of signing and decryption this file needs to contain the
user's private key as well as his certificate.
.Pp
For message signing
.Ql USER@HOST
is always derived from the value of
.Va from
(or, if that contains multiple addresses,
.Va sender ) .
For the purpose of encryption the recipient's public encryption key
(certificate) is expected; the command
.Ic certsave
can be used to save certificates of signed messages (the section
.Sx "Signed and encrypted messages with S/MIME"
gives some details).
This mode of operation is usually driven by the specialized form.
.Pp
When decrypting messages the account is derived from the recipient
fields
.Pf ( Ql To:
and
.Ql Cc: )
of the message, which are searched for addresses for which such
a variable is set.
\*(UA always uses the first address that matches,
so if the same message is sent to more than one of the user's addresses
using different encryption keys, decryption might fail.
.
.Mx Va smime-sign-include-certs
.It Va smime-sign-include-certs-USER@HOST , smime-sign-include-certs
\*(OP If used, this is supposed to a consist of a comma-separated list
of files, each of which containing a single certificate in PEM format to
be included in the S/MIME message in addition to the
.Va smime-sign-cert
certificate.
This is most useful for long certificate chains if it is desired to aid
the receiving party's verification process.
Note that top level certificates may also be included in the chain but
don't play a role for verification.
Also see
.Va smime-sign-cert .
Remember that for this
.Ql USER@HOST
refers to the variable
.Va from
(or, if that contains multiple addresses,
.Va sender ) .
.
.Mx Va smime-sign-message-digest
.It Va smime-sign-message-digest-USER@HOST , smime-sign-message-digest
\*(OP Specifies the message digest to use when signing S/MIME messages.
RFC 5751 mandates a default of
.Ql sha1 .
Possible values are (case-insensitive and) in decreasing cipher strength:
.Ql sha512 ,
.Ql sha384 ,
.Ql sha256 ,
.Ql sha224
and
.Ql md5 .
.Pp
The actually available message digest algorithms depend on the
cryptographic library that \*(UA uses.
\*(OP Support for more message digest algorithms may be available
through dynamic loading via, e.g.,
.Xr EVP_get_digestbyname 3
(OpenSSL) if \*(UA has been compiled to support this.
Remember that for this
.Ql USER@HOST
refers to the variable
.Va from
(or, if that contains multiple addresses,
.Va sender ) .
.
.Mx
.It Va smtp
\*(OP Normally \*(UA invokes the program defined via
.Va sendmail
to transfer messages, as described in
.Sx "Sending mail" .
Setting the
.Va \&\&smtp
variable will instead cause SMTP network connections be made to the
server specified therein in order to directly submit the message.
\*(UA knows about three different
.Dq SMTP protocols :
.Pp
.Bl -bullet -compact
.It
The plain SMTP protocol (RFC 5321) that normally lives on the
server port 25 and requires setting the
.Va smtp-use-starttls
variable to enter a SSL/TLS encrypted session state.
Assign a value like \*(IN
.Ql [smtp://][user[:password]@]server[:port]
(\*(OU
.Ql [smtp://]server[:port] )
to choose this protocol.
.It
Then the so-called SMTPS which is supposed to live on server port 465
and is automatically SSL/TLS secured.
Unfortunately it never became a standardized protocol and may thus not
be supported by your hosts network service database
\(en in fact the port number has already been reassigned to other
protocols!
.Pp
SMTPS is nonetheless a commonly offered protocol and thus can be
chosen by assigning a value like \*(IN
.Ql smtps://[user[:password]@]server[:port]
(\*(OU
.Ql smtps://server[:port] ) ;
due to the mentioned problems it is usually necessary to explicitly
specify the port as
.Ql :465 ,
however.
.It
Finally there is the SUBMISSION protocol (RFC 6409), which usually
lives on server port 587 and is practically identically to the SMTP
protocol from \*(UAs point of view beside that; it requires setting the
.Va smtp-use-starttls
variable to enter a SSL/TLS secured session state.
Assign a value like \*(IN
.Ql submission://[user[:password]@]server[:port]
(\*(OU
.Ql submission://server[:port] ) .
.El
.Pp
For more on credentials etc. please see
.Sx "On URL syntax and credential lookup" .
The SMTP transfer is executed in a child process, which runs
asynchronously unless either the
.Va sendwait
or the
.Va verbose
variable is set.
If it receives a TERM signal, it will abort and save the message to
.Ev DEAD .
.
.Mx Va smtp-auth
.It Va smtp-auth-USER@HOST , smtp-auth-HOST , smtp-auth
\*(OP Variable chain that sets the SMTP authentication method.
Possible values are
.Ql none
(\*(OU default),
.Ql plain
(\*(IN default),
.Ql login
as well as the \*(OPal methods
.Ql cram-md5
and
.Ql gssapi .
The
.Ql none
method doesn't need any user credentials,
.Ql gssapi
requires a user name and all other methods require a user name and
a password.
See \*(IN
.Va smtp ,
.Va user
and
.Va password
(\*(OU
.Va smtp-auth-password
and
.Va smtp-auth-user ) .
Note that
.Va smtp-auth-HOST
is \*(IN.
\*(OU: Note for
.Va smtp-auth-USER@HOST :
may override dependend on sender address in the variable
.Va from .
.
.It Va smtp-auth-password
\*(OP \*(OU Sets the global fallback password for SMTP authentication.
If the authentication method requires a password, but neither
.Va smtp-auth-password
nor a matching
.Va smtp-auth-password-USER@HOST
can be found,
\*(UA will ask for a password on the user's terminal.
.
.It Va smtp-auth-password-USER@HOST
\*(OU Overrides
.Va smtp-auth-password
for specific values of sender addresses, dependent upon the variable
.Va from .
.
.It Va smtp-auth-user
\*(OP \*(OU Sets the global fallback user name for SMTP authentication.
If the authentication method requires a user name, but neither
.Va smtp-auth-user
nor a matching
.Va smtp-auth-user-USER@HOST
can be found,
\*(UA will ask for a user name on the user's terminal.
.
.It Va smtp-auth-user-USER@HOST
\*(OU Overrides
.Va smtp-auth-user
for specific values of sender addresses, dependent upon the variable
.Va from .
.
.Mx
.It Va smtp-hostname
\*(IN Normally \*(UA uses the variable
.Va from
to derive the necessary
.Ql USER@HOST
information to issue a
.Ql MAIL FROM:<>
SMTP command.
Setting
.Va smtp-hostname
can be used to use the
.Ql USER
from the SMTP account
.Pf ( Va smtp
or the
.Va user
variable chain)
and the
.Ql HOST
from the content of this variable (or, if that is the empty string,
.Va hostname
or the local hostname as a last resort).
This often allows using an address that is itself valid but hosted by
a provider other than which (in
.Va from )
is about to send the message.
Setting this variable also influences the generated
.Ql Message-ID: .
.
.
.Mx
.It Va spam-interface
\*(OP In order to use any of the spam-related commands (like, e.g.,
.Ic spamrate )
the desired spam interface must be defined by setting this variable.
Please refer to the manual section
.Sx "Handling spam"
for the complete picture of spam handling in \*(UA.
All or none of the following interfaces may be available:
.
.Bl -tag -width ".It Ql _ilte_"
.It Ql spamc
Interaction with
.Xr spamc 1
from the
.Xr spamassassin 1
.Pf ( Lk http://spamassassin.apache.org SpamAssassin )
suite.
Different to the generic filter interface \*(UA will automatically add
the correct arguments for a given command and has the necessary
knowledge to parse the program's output.
A default value for
.Va spamc-command
will have been compiled into the \*(UA binary if
.Xr spamc 1
has been found in
.Ev PATH
during compilation.
Shall it be necessary to define a specific connection type (rather than
using a configuration file for that), the variable
.Va spamc-arguments
can be used as in, e.g.,
.Ql -d server.example.com -p 783 .
It is also possible to specify a per-user configuration via
.Va spamc-user .
Note that this interface doesn't inspect the
.Ql is-spam
flag of a message for the command
.Ic spamforget .
.
.It Ql spamd
\*(UA will directly communicate with the
.Xr spamassassin 1
daemon
.Xr spamd 1
via a path-based
.Xr unix 4
stream socket as specified in
.Va spamd-socket .
It is possible to specify a per-user configuration via
.Va spamd-user .
.
.It Ql filter
generic spam filter support via freely configurable hooks.
This interface is ment for programs like
.Xr bogofilter 1
and
.Xr sylfilter 1
and requires according behaviour in respect to the hooks' exit
status for at least the command
.Ic spamrate
.Pf ( Ql 0
meaning a message is spam,
.Ql 1
for non-spam,
.Ql 2
for unsure and any other return value indicating a hard error);
since the hooks can include shell code snippets diverting behaviour
can be intercepted as necessary.
The hooks are
.Va spamfilter-ham , spamfilter-noham , spamfilter-nospam , \
  spamfilter-rate
and
.Va spamfilter-spam ;
the manual section
.Sx "Handling spam"
contains examples for some programs.
The process environment of the hooks will have the variables
.Ev NAIL_TMPDIR , TMPDIR
and
.Ev NAIL_FILENAME_GENERATED
set.
Note that spam score support for
.Ic spamrate
isn't supported unless the \*(OPtional regular expression support is
available and the
.Va spamfilter-rate-scanscore
variable is set.
.El
.
.
.Mx
.It Va spam-maxsize
\*(OP Messages that exceed this size won't be passed through to the
configured
.Va spam-interface .
The default is 420000 bytes.
.
.Mx
.It Va spamc-command
\*(OP The path to the
.Xr spamc 1
program for the
.Ql spamc
.Va spam-interface .
Note that the path is not expanded, but used
.Dq as is .
A fallback path will have been compiled into the \*(UA binary if the
executable had been found during compilation.
.
.Mx
.It Va spamc-arguments
\*(OP Even though \*(UA deals with most arguments for the
.Ql spamc
.Va spam-interface
automatically, it may at least sometimes be desirable to specifiy
connection-related ones via this variable, e.g.,
.Ql -d server.example.com -p 783 .
.
.Mx
.It Va spamc-user
\*(OP Specify a username for per-user configuration files for the
.Ql spamc
.Va spam-interface .
If this is set to the empty string then \*(UA will use the name of the
current
.Va user .
.
.Mx
.It Va spamd-socket
\*(OP Specify the path of the
.Xr unix 4
domain socket on which
.Xr spamd 1
listens for connections for the
.Ql spamd
.Va spam-interface .
Note that the path is not expanded, but used
.Dq as is .
.
.Mx
.It Va spamd-user
\*(OP Specify a username for per-user configuration files for the
.Ql spamd
.Va spam-interface .
If this is set to the empty string then \*(UA will use the name of the
current
.Va user .
.
.Mx
.Mx
.Mx
.Mx
.Mx
.It Va spamfilter-ham , spamfilter-noham , \
  spamfilter-nospam , spamfilter-rate , spamfilter-spam
\*(OP Command and argument hooks for the
.Ql filter
.Va spam-interface .
The manual section
.Sx "Handling spam"
contains examples for some programs.
.
.Mx
.It Va spamfilter-rate-scanscore
\*(OP Because of the generic nature of the
.Ql filter
.Va spam-interface
spam scores are not supported for it by default, but if the \*(OPtional
regular expression support is available then setting this variable can
be used to overcome this restriction.
It is interpreted as follows: first a number (digits) is parsed that
must be followed by a semicolon
.Ql \&;
and a regular expression.
Then the latter is used to parse the first output line of the
.Va spamfilter-rate
hook, and, in case the evaluation is successful, the group that has been
specified via the number is interpreted as a floating point scan score.
.
.Mx
.It Va ssl-ca-dir
\*(OP Specifies a directory with CA certificates in PEM (Pricacy
Enhanced Mail) for verification of of SSL/TLS server certificates.
See
.Xr SSL_CTX_load_verify_locations 3
for more information.
.
.Mx
.It Va ssl-ca-file
\*(OP Specifies a file with CA certificates in PEM format for
verification of SSL/TLS server certificates.
See
.Xr SSL_CTX_load_verify_locations 3
for more information.
.
.Mx Va ssl-cert
.It Va ssl-cert-USER@HOST , ssl-cert-HOST , ssl-cert
\*(OP Variable chain that sets the file name for a SSL/TLS client
certificate required by some servers.
This is a direct interface to the
.Ql Certificate
slot of the
.Xr SSL_CONF_cmd 3
function of the OpenSSL library, if available.
.
.Mx Va ssl-cipher-list
.It Va ssl-cipher-list-USER@HOST , ssl-cipher-list-HOST , ssl-cipher-list
\*(OP Specifies a list of ciphers for SSL/TLS connections.
This is a direct interface to the
.Ql CipherString
slot of the
.Xr SSL_CONF_cmd 3
function of the OpenSSL library, if available; see
.Xr ciphers 1
for more information.
By default \*(UA doesn't set a list of ciphers, which in effect will use a
.Va ssl-protocol
specific cipher (protocol standards ship with a list of acceptable
ciphers), possibly cramped to what the actually used SSL/TLS library
supports \(en the manual section
.Sx "An example configuration"
also contains a SSL/TLS use case.
.
.Mx
.It Va ssl-config-file
\*(OP If this variable is set \*(UA will call
.Xr CONF_modules_load_file 3
to allow OpenSSL to be configured according to the host system wide
security settings.
If a non-empty value is given then this will be used to specify the
configuration file to be used instead of the global OpenSSL default;
note that in this case it is an error if the file cannot be loaded.
The application name will always be passed as
.Dq \*(ua .
.
.Mx
.It Va ssl-crl-file
\*(OP Specifies a file that contains a CRL in PEM format to use when
verifying SSL/TLS server certificates.
.
.Mx
.It Va ssl-crl-dir
\*(OP Specifies a directory that contains files with CRLs in PEM format
to use when verifying SSL/TLS server certificates.
.
.Mx Va ssl-key
.It Va ssl-key-USER@HOST , ssl-key-HOST , ssl-key
\*(OP Variable chain that sets the file name for the private key of
a SSL/TLS client certificate.
If unset, the name of the certificate file is used.
The file is expected to be in PEM format.
This is a direct interface to the
.Ql PrivateKey
slot of the
.Xr SSL_CONF_cmd 3
function of the OpenSSL library, if available.
.
.Mx Va ssl-method
.It Va ssl-method-USER@HOST , ssl-method-HOST , ssl-method
\*(OP
\*(OB Please use the newer and more flexible
.Va ssl-protocol
instead: if both values are set,
.Va ssl-protocol
will take precedence!
Can be set to the following values, the actually used
.Va ssl-protocol
specification to which it is mapped is shown in parenthesis:
.Ql tls1.2
.Pf ( Ql -ALL, TLSv1.2 ) ,
.Ql tls1.1
.Pf ( Ql -ALL, TLSv1.1 ) ,
.Ql tls1
.Pf ( Ql -ALL, TLSv1 )
and
.Ql ssl3
.Pf ( Ql -ALL, SSLv3 ) ;
the special value
.Ql auto
is mapped to
.Ql ALL, -SSLv2
and thus includes the SSLv3 protocol.
Note that SSLv2 is no longer supported at all.
.
.Mx Va ssl-protocol
.It Va ssl-protocol-USER@HOST , ssl-protocol-HOST , ssl-protocol
\*(OP Specify the used SSL/TLS protocol.
This is a direct interface to the
.Ql Protocol
slot of the
.Xr SSL_CONF_cmd 3
function of the OpenSSL library, if available;
otherwise an \*(UA internal parser is used which understands the
following subset of (case-insensitive) command strings:
.Ql SSLv3 ,
.Ql TLSv1 ,
.Ql TLSv1.1
and
.Ql TLSv1.2 ,
as well as the special value
.Ql ALL .
Multiple specifications may be given via a comma-separated list which
ignores any whitespace.
An optional
.Ql +
plus prefix will enable a protocol, a
.Ql -
minus prefix will disable it, so that
.Ql -ALL, TLSv1.2
will enable only the TLSv1.2 protocol.
.Pp
It depends upon the used TLS/SSL library which protocols are actually
supported and which protocols are used if
.Va ssl-protocol
is not set, but note that SSLv2 is no longer supported at all and
actively disabled.
Especially for older protocols explicitly securing
.Va ssl-cipher-list
may be worthwile, see
.Sx "An example configuration" .
.
.Mx
.It Va ssl-rand-egd
\*(OP Gives the pathname to an entropy daemon socket, see
.Xr RAND_egd 3 .
Not all SSL/TLS libraries support this.
.
.Mx
.It Va ssl-rand-file
\*(OP Gives the pathname to a file with entropy data, see
.Xr RAND_load_file 3 .
If the file is a regular file writable by the invoking user,
new data is written to it after it has been loaded.
.
.Mx Va ssl-verify
.It Va ssl-verify-USER@HOST , ssl-verify-HOST , ssl-verify
\*(OP Variable chain that sets the action to be performed if an error
occurs during SSL/TLS server certificate validation.
Valid (case-insensitive) values are
.Ql strict
(fail and close connection immediately),
.Ql ask
(ask whether to continue on standard input),
.Ql warn
(print a warning and continue),
.Ql ignore
(do not perform validation).
The default is
.Ql ask .
.
.Mx
.It Va stealthmua
If only set without an assigned value, then this option inhibits the
generation of the
.Ql Message-ID:
and
.Ql User-Agent:
header fields that include obvious references to \*(UA.
There are two pitfalls associated with this:
First, the message id of outgoing messages is not known anymore.
Second, an expert may still use the remaining information in the header
to track down the originating mail user agent.
If set to the value
.Ql noagent ,
then the mentioned
.Ql Message-ID:
suppression doesn't occur.
.
.Mx
.It Va toplines
If defined, gives the number of lines of a message to be printed out
with the top command; normally, the first five lines are printed.
.
.Mx
.It Va ttycharset
The character set of the terminal \*(UA operates on,
and the one and only supported character set that \*(UA can use if no
character set conversion capabilities have been compiled into it,
in which case it defaults to ISO-8859-1 unless it can deduce a value
from the
.Ev LC_CTYPE
locale environment.
Refer to the section
.Sx "Character sets"
for the complete picture about character sets.
.
.Mx Va user
.It Va user-HOST , user
\*(IN Variable chain that sets a global fallback user name, which is
used in case none has been given in the protocol and account-specific
URL.
This variable defaults to the value of
.Ev USER .
.
.Mx
.Mx
.Mx
.Mx
.It Va version , version-major , version-minor , version-update
\*(RO \*(UA version information: the first variable contains a string
containing the complete version identification \(en this is identical to
the output of the command
.Ic version .
The latter three contain only digits: the major, minor and update
version numbers.
.El
.\" }}}
.\" }}} (Variable options)
.
.
.\" .Sh ENVIRONMENT {{{
.Sh ENVIRONMENT
.
The term
.Dq environment variable
should be considered an indication that the following variables are
either standardized as being vivid parts of process environments, or
are commonly found in there.
Unless otherwise explicitly noted they integrate into the normal
variable handling, as documented above, from \*(UAs point of view.
.
.Bl -tag -width ".It Ev _AILR_"
.Mx
.It Ev COLUMNS
The user's preferred width in column positions for the terminal screen
or window.
Queried and used once on program startup.
.
.Mx
.It Ev DEAD
The name of the file to use for saving aborted messages if
.Va save
is set; this defaults to
.Pa dead.letter
in the user's
.Ev HOME
directory.
.
.Mx
.It Ev EDITOR
Pathname of the text editor to use in the
.Ic edit
command and
.Ic ~e
.Sx "TILDE ESCAPES" .
A default editor is used if this value is not defined.
.
.Mx
.It Ev HOME
The user's home directory.
This variable is only used when it resides in the process environment.
Use
.Ic setenv
to update the value at runtime.
.
.Mx
.Mx
.Mx
.Mx
.Mx
.It Ev LANG , LC_ALL , LC_COLLATE , LC_CTYPE , LC_MESSAGES
See
.Xr locale 7
and
.Sx "Character sets" .
.
.Mx
.It Ev LINES
The user's preferred number of lines on a page or the vertical screen
or window size in lines.
Queried and used once on program startup.
.
.Mx
.It Ev LISTER
Pathname of the directory lister to use in the
.Ic folders
command when operating on local mailboxes.
Default is
.Xr ls 1
(path search through
.Ev SHELL ) .
.
.Mx
.It Ev MBOX
The name of the user's mbox file.
Supports a logical subset of the special conventions that are
documented for the
.Ic file
command and the
.Va folder
option.
The fallback default is
.Pa mbox
in the user's
.Ev HOME
directory.
.
.It Ev MAIL
Is used as the user's primary system mailbox, unless
.Va inbox
is set, see
.Ic file .
This is assumed to be an absolute pathname.
.
.Mx
.It Ev MAILRC
Is used as a startup file instead of
.Pa \*(ur
if set.
When \*(UA scripts are invoked on behalf of other users,
this variable should be set to
.Pa /dev/null
to avoid side-effects from reading their configuration files.
This variable is only used when it resides in the process environment.
.
.Mx
.It Ev NAIL_NO_SYSTEM_RC
If this variable is set then reading of
.Pa \*(UR
at startup is inhibited, i.e., the same effect is achieved as if \*(UA
had been started up with the option
.Fl n .
This variable is only used when it resides in the process environment.
.
.Mx
.It Ev NETRC
\*(IN \*(OP This variable overrides the default location of the user's
.Pa .netrc
file.
.
.Mx
.It Ev PAGER
Pathname of the program to use in the more command or when the
.Va crt
variable is set.
The default paginator is
.Xr more 1
(path search through
.Ev SHELL ) .
.
.Mx
.It Ev PATH
A list of directories that is searched by the shell when looking for
commands (as such only recognized in the process environment).
.
.Mx
.It Ev SHELL
The shell to use for the commands
.Ic \&! ,
.Ic shell ,
the
.Ic ~!
.Sx "TILDE ESCAPES"
and when starting subprocesses.
A default shell is used if this option is not defined.
.
.Mx
.It Ev SYSV3
Changes the letters printed in the first column of a header summary.
.
.Mx
.It Ev TERM
\*(OP The terminal type for which output is to be prepared.
.
.Mx
.It Ev TMPDIR
Used as directory for temporary files instead of
.Pa /tmp ,
if set.
This variable is only used when it resides in the process environment.
Use
.Ic setenv
to update the value at runtime.
.
.Mx
.It Ev USER
Force identification as the given user, i.e., identical to the
.Fl u
command line option.
This variable is only used when it resides in the process environment.
Use
.Ic setenv
to update the value at runtime, but note that doing so won't trigger any
of those validation checks that were performed on program startup (again).
.
.Mx
.It Ev VISUAL
Pathname of the text editor to use in the
.Ic visual
command and
.Ic ~v
.Sx "TILDE ESCAPES" .
.El
.\" }}}
.
.
.\" .Sh FILES {{{
.Sh FILES
.
.Bl -tag -width ".It Pa _etc/mime.type_"
.It Pa \*(ur
File giving initial commands.
.
.It Pa \*(UR
System wide initialization file.
.
.Mx
.It Pa ~/.mime.types
Personal MIME types, see
.Sx "The mime.types files" .
.
.Mx
.It Pa /etc/mime.types
System wide MIME types, see
.Sx "The mime.types files" .
.
.Mx
.It Pa ~/.netrc
\*(IN \*(OP The default location of the users
.Pa .netrc
file \(en the section
.Sx "The .netrc file"
documents the file format.
.El
.
.\" .Ss "The mime.types files" {{{
.Ss "The mime.types files"
.
When sending messages \*(UA tries to determine the content type of all
attachments.
When displaying message content or attachments \*(UA uses the content
type to decide whether it can directly display data or whether it needs to
deal with content handlers, as can be defined via
.Va pipe-TYPE/SUBTYPE
(and
.Va pipe-EXTENSION )
variables, to do so.
.
.Pp
It learns about MIME types and how to treat them by reading
.Pa mime.types
files, the loading of which can be controlled by setting the variable
.Va mimetypes-load-control .
(The command
.Ic mimetype
can also be used to deal with MIME types.)
.Pa mime.types
files have the following syntax:
.
.Pp
.Dl type/subtype extension [extension ...]
.
.Pp
where
.Ql type/subtype
are strings describing the file contents, and one or multiple
.Ql extension Ns
s, separated by whitespace, name the part of a filename starting after
the last dot (of interest).
Comments may be introduced anywhere on a line with a number sign
.Ql # ,
causing the remaining line to be discarded.
.
\*(UA also supports an extended, non-portable syntax in specially
crafted files, which can be loaded via the alternative value syntax of
.Va mimetypes-load-control
and prepends an optional
.Ql type-marker :
.
.Pp
.Dl [type-marker ]type/subtype extension [extension ...]
.
.Pp
The following type markers are supported:
.
.Pp
.Bl -tag -compact -offset indent -width ".It Ar _n_u"
.It Ar @
Treat message parts with this content as plain text.
.It Ar @t@
The same as plain
.Ar @ .
.It Ar @h@
Treat message parts with this content as HTML tagsoup.
If the \*(OPal HTML-tagsoup-to-text converter is not available treat
the content as plain text instead.
.It Ar @H@
Likewise
.Ar @h@
but instead of falling back to plain text require an explicit content
handler to be defined.
.El
.
.Pp
Further reading:
for sending messages:
.Va mime-allow-text-controls .
For reading etc. messages:
.Sx "Viewing HTML mail and MIME attachments" ,
.Va mime-counter-evidence ,
.Va pipe-TYPE/SUBTYPE ,
.Va pipe-EXTENSION .
.\" }}}
.
.\" .Ss "The .netrc file" {{{
.Ss "The .netrc file"
.
The
.Pa .netrc
file contains user credentials for machine accounts.
The default location in the user's
.Ev HOME
directory may be overridden by the
.Ev NETRC
environment variable.
The file consists of space, tabulator or newline separated tokens.
\*(UA implements a parser that supports a superset of the original BSD
syntax, but users should nonetheless be aware of portability glitches
of that file format, shall their
.Pa .netrc
be usable across multiple programs and platforms:
.
.Pp
.Bl -bullet -compact
.It
BSD doesn't support single, but only double quotation marks, e.g.,
.Ql password="pass with spaces" .
.It
BSD (only?) supports escaping of single characters via a backslash
(e.g., a space can be escaped via
.Ql \e\0 ) ,
in- as well as outside of a quoted string.
.It
BSD doesn't require the final quotation mark of the final user input token.
.It
At least Hewlett-Packard seems to support a format which also allows
tokens to be separated with commas \(en this format is not supported!
.It
Whereas other programs may require that the
.Pa .netrc
file is accessible by only the user if it contains a
.Cd password
token for any other
.Cd login
than
.Dq anonymous ,
\*(UA will always require these strict permissions.
.El
.
.Pp
Of the following list of supported tokens \*(UA only uses (and caches)
.Cd machine ,
.Cd login
and
.Cd password :
.
.Bl -tag -width password
.It Cd machine Ar name
The hostname of the entries' machine, lowercase-normalized by \*(UA
before use.
Any further file content, until either end-of-file or the occurrence
of another
.Cd machine
or a
.Cd default
first-class token is bound (only related) to the machine
.Ar name .
.Pp
As an extension that shouldn't be the cause of any worries
\*(UA supports a single wildcard prefix for
.Ar name :
.Bd -literal -offset indent
machine *.example.com login USER password PASS
machine pop3.example.com login USER password PASS
machine smtp.example.com login USER password PASS
.Ed
.Pp
which would match
.Ql xy.example.com
as well as
.Ql pop3.example.com ,
but neither
.Ql example.com
nor
.Ql local.smtp.example.com .
Note that in the example neither
.Ql pop3.example.com
nor
.Ql smtp.example.com
will be matched by the wildcard, since the exact matches take
precedence (it is however faster to specify it the other way around).
.
.It Cd default
This is the same as
.Cd machine
except that it is a fallback entry that is used shall none of the
specified machines match; only one default token may be specified,
and it must be the last first-class token.
.
.It Cd login Ar name
The user name on the remote machine.
.
.It Cd password Ar string
The user's password on the remote machine.
.
.It Cd account Ar string
Supply an additional account password.
This is merely for FTP purposes.
.
.It Cd macdef Ar name
Define a macro.
A macro is defined with the specified
.Ar name ;
it is formed from all lines beginning with the next line and continuing
until a blank line is (consecutive newline characters are) encountered.
(Note that
.Cd macdef
entries cannot be utilized by multiple machines, too, but must be
defined following the
.Ic machine
they are intended to be used with.)
If a macro named
.Ar init
exists, it is automatically run as the last step of the login process.
This is merely for FTP purposes.
.El
.\" }}}
.
.\" }}}
.
.
.\" .Sh EXAMPLES {{{
.Sh EXAMPLES
.
.\" .Ss "An example configuration" {{{
.Ss "An example configuration"
.
.Bd -literal -offset indent
# This example assumes v15.0 compatibility mode
set v15-compat

# Where are the up-to-date SSL certificates?
#set ssl-ca-dir=/etc/ssl/certs
set ssl-ca-file=/etc/ssl/certs/ca-certificates.crt

# (Since we manage up-to-date ones explicitly, don't use any,
# possibly outdated, default certificates shipped with OpenSSL
set ssl-no-default-ca

# Don't use protocols olders than TLS v1.2.
# Change this only when the remote server doesn't support it:
# maybe use ssl-protocol-HOST (or -USER@HOST) syntax to define
# such explicit exceptions, then
set ssl-protocol="-ALL,+TLSv1.2"

# Explicitly define the list of ciphers, which may improve security,
# especially with protocols older than TLS v1.2.  See ciphers(1).
# Hint: it is important to include "@STRENGTH": only with it the
# final list will be sorted by algorithm strength.
# This is an example: in reality it is possibly best to only use
# ssl-cipher-list-HOST (or -USER@HOST), as necessary, again..
set ssl-cipher-list="ALL:!aNULL:!MEDIUM:!LOW:\e
    !MD5:!RC4:!EXPORT:@STRENGTH"

# Request strict transport security checks!
set ssl-verify=strict

# Essential setting: select allowed character sets
set sendcharsets=utf-8,iso-8859-1

# A very kind option: when replying to a message, first try to
# use the same encoding that the original poster used herself!
set reply-in-same-charset

# When replying to or forwarding a message the comment and name
# parts of email addresses are removed unless this variable is set
set fullnames

# When sending messages, wait until the Mail-Transfer-Agent finishs.
# Only like this you'll be able to see errors reported through the
# exit status of the MTA (including the builtin SMTP one)!
set sendwait

# Only use builtin MIME types, no mime.types(5) files
set mimetypes-load-control

# Default directory where we act in (relative to $HOME)
set folder=mail MBOX=+mbox.mbox record=+sent.mbox \e
    DEAD=+dead.mbox

# Make "file mymbox" and "file myrec" go to..
shortcut mymbox %:+mbox.mbox myrec +sent.mbox

# Not really optional, e.g., for S/MIME
set from="Your Name <youremail@domain>"

# It may be necessary to set hostname and/or smtp-hostname
# if the "SERVER" of smtp and "domain" of from don't match.
# The `urlencode' command can be used to encode USER and PASS
set smtp=(smtp[s]/submission)://[USER[:PASS]@]SERVER[:PORT] \e
    smtp-auth=login/plain... \e
    smtp-use-starttls

# Never refuse to start into interactive mode, and more
set emptystart \e
    colour-pager crt= followup-to followup-to-honour=ask-yes \e
    history-gabby mime-counter-evidence=6 \e
    prompt="\e033[31m?\e?[\e$ \e@]\e& \e033[0m" \e
    NAIL_HISTFILE=+.s-nailhist NAIL_HISTSIZE=-1 \e
    reply-to-honour=ask-yes

# When `p'rinting messages, show only these headers
# (use `P'rint for all headers and `S'how for raw message)
retain date from to cc subject

# Some mailing lists
mlist @xyz-editor.xyz$ @xyzf.xyz$
mlsubscribe ^xfans@xfans.xyz$

# A real life example of a very huge free mail provider
account XooglX {
  localopts yes
  set from="Your Name <youremail@domain>"
  # (The plain smtp:// proto is optional)
  set smtp=USER:PASS@smtp.gmXil.com smtp-use-starttls
}

# Here is a pretty large one which does not allow sending mails
# if there is a domain name mismatch on the SMTP protocol level,
# which would bite us if the value of from does not match, e.g.,
# for people who have a sXXXXeforge project and want to speak
# with the mailing list under their project account (in from),
# still sending the message through their normal mail provider
account XandeX {
  localopts true
  set from="Your Name <youremail@domain>"
  set smtp=smtps://USER:PASS@smtp.yaXXex.ru:465 \e
      hostname=yaXXex.com smtp-hostname=
}

# Create some new commands so that, e.g., `ls /tmp' will..
ghost l   !ls -aFtr
ghost L   !ls -aFt
ghost ll  !ls -aFltr
ghost Ll  !ls -aFlt
ghost la  !ls -aFr
ghost La  !ls -aF
ghost lla !ls -aFlr
ghost Lla !ls -aFl
ghost lS  !ls -aFrS
ghost LS  !ls -aFS
ghost llS !ls -aFlrS
ghost LlS !ls -aFlS

# We don't support gpg(1) directly yet.  But simple --clearsign'd
# message parts can be dealt with as follows:
define V {
  localopts yes
  set pipe-text/plain="set -C;\e
    : > \e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e" \e
    trap \e"rm -f \e\e\e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e\e\e"\e" \e
      EXIT INT QUIT PIPE TERM;\e
    set +C;\e
    cat > \e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e";\e
    < \e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e" awk \e
        -v TMPFILE=\e"${TMPDIR}/${NAIL_FILENAME_GENERATED}\e" '\e
      BEGIN {done=0}\e
      /^-----BEGIN PGP SIGNED MESSAGE-----/,/^$/ {\e
        if (done++ != 0)\e
          next;\e
        print \e"--- GPG --verify ---\e";\e
        system(\e"gpg --verify \e" TMPFILE \e" 2>&1\e");\e
        print \e"--- GPG --verify ---\e";\e
        print \e"\e";\e
        next;\e
      }\e
      /^-----BEGIN PGP SIGNATURE-----/,\e
          /^-----END PGP SIGNATURE-----/ {\e
        next;\e
      }\e
      {print}\e
      '"
  print
}
ghost V call V

define RK {
  !printf 'Key IDs to gpg --recv-keys: ';\e
    read keyids;\e
    gpg --recv-keys ${keyids};
}
ghost RK call RK
.Ed
.
.Pp
When storing passwords in
.Pa \*(ur
appropriate permissions should be set on this file with
.Ql $ chmod 0600 \*(ur .
If the \*(OPal
.Va netrc-lookup
is available user credentials can be stored in the central
.Pa .netrc
file instead; e.g., here is a different version of the example account
that sets up SMTP and POP3:
.
.Bd -literal -offset indent
account XandeX {
  localopts true
  set from="Your Name <youremail@domain>"
  set netrc-lookup
  #set agent-shell-lookup="gpg -d .pass.gpg"

  set smtp=smtps://smtp.yXXXXx.ru:465 \e
      smtp-hostname= hostname=yXXXXx.com
  set pop3-keepalive=240 pop3-no-apop-pop.yXXXXx.ru
  ghost xp fi pop3s://pop.yXXXXx.ru
}
.Ed
.
.Pp
and, in the
.Pa .netrc
file:
.
.Bd -literal -offset indent
machine *.yXXXXx.ru login USER password PASS
.Ed
.
.Pp
If the also \*(OPal
.Va agent-shell-lookup
is available things could be diversified further by using encrypted
password storage: for this, don't specify
.Ql password PASS
in the
.Pa .netrc
file and instead uncomment the line that defines agent lookup in the
example
.Ic account
above, then create the encrypted password storage file
.Pa .pass.gpg :
.
.Bd -literal -offset indent
$ echo PASS > .pass
$ gpg -e .pass
$ eval `gpg-agent --daemon \e
        --pinentry-program=/usr/bin/pinentry-curses \e
        --max-cache-ttl 99999 --default-cache-ttl 99999`
.Ed
.
.Pp
This configuration should now work just fine (use the
.Fl d
command line option for a(n almost) dry-run):
.
.Pp
.Dl $ echo text | \*(ua -vv -AXandeX -s Subject some@where
.\" }}}
.
.\" .Ss "Signed and encrypted messages with S/MIME" {{{
.Ss "Signed and encrypted messages with S/MIME"
.
\*(OP S/MIME provides two central mechanisms:
message signing and message encryption.
A signed message contains some data in addition to the regular text.
The data can be used to verify that the message was sent using a valid
certificate, that the sender's address in the message header matches
that in the certificate, and that the message text has not been altered.
Signing a message does not change its regular text;
it can be read regardless of whether the recipient's software is able to
handle S/MIME.
.
.Pp
It is thus usually possible to sign all outgoing messages if so desired.
Encryption, in contrast, makes the message text invisible for all people
except those who have access to the secret decryption key.
To encrypt a message, the specific recipient's public encryption key
must be known.
It is therefore not possible to send encrypted mail to people unless their
key has been retrieved from either previous communication or public key
directories.
A message should always be signed before it is encrypted.
Otherwise, it is still possible that the encrypted message text is
altered.
.
.Pp
A central concept to S/MIME is that of the certification authority (CA).
A CA is a trusted institution that issues certificates.
For each of these certificates it can be verified that it really
originates from the CA, provided that the CA's own certificate is
previously known.
A set of CA certificates is usually delivered with OpenSSL and installed
on your system.
If you trust the source of your OpenSSL software installation,
this offers reasonable security for S/MIME on the Internet.
(Otherwise set
.Va ssl-no-default-ca
and use
.Va smime-ca-file
and/or
.Va smime-ca-dir . )
In general, a certificate cannot be more secure than the method its CA
certificate has been retrieved with, though.
Thus if you download a CA certificate from the Internet,
you can only trust the messages you verify using that certificate as
much as you trust the download process.
.
.Pp
The first thing you need for participating in S/MIME message exchange is
your personal certificate, including a private key.
The certificate contains public information, in particular your name and
your email address(es), and the public key that is used by others to
encrypt messages for you,
and to verify signed messages they supposedly received from you.
The certificate is included in each signed message you send.
The private key must be kept secret.
It is used to decrypt messages that were previously encrypted with your
public key, and to sign messages.
.
.Pp
For personal use it is recommended that you get a S/MIME certificate
from one of the major CAs on the Internet using your WWW browser.
Many CAs offer such certificates for free.
There is also
.Lk https://www.CAcert.org
which issues client and server certificates to members of their
community for free; their root certificate
.Pf ( Lk https://\:www.cacert.org/\:certs/\:root.crt )
is often not in the default set of trusted CA root certificates, though,
which means you will have to download their root certificate separately
and ensure it is part of our S/MIME certificate validation chain by
including it in
.Va smime-ca-dir
or as a vivid member of the
.Va smime-ca-file .
But let's take a step-by-step tour on how to setup S/MIME with
a certificate from CAcert.org despite this situation!
.
.Pp
First of all you will have to become a member of the CAcert.org
community, simply by registrating yourself via the web interface.
Once you are, create and verify all email addresses you want to be able
to create signed and encrypted messages for/with using the corresponding
entries of the web interface.
Now ready to create S/MIME certificates, so let's create a new
.Dq client certificate ,
ensure to include all email addresses that should be covered by the
certificate in the following web form, and also to use your name as the
.Dq common name .
.
.Pp
Create a private key and a certificate request on your local computer
(please see the manual pages of the used commands for more in-depth
knowledge on what the used arguments etc. do):
.
.Pp
.Dl openssl req -nodes -newkey rsa:4096 -keyout key.pem -out creq.pem
.
.Pp
Afterwards copy-and-paste the content of
.Dq creq.pem
into the certificate-request (CSR) field of the web form on the
CAcert.org website (you may need to unfold some
.Dq advanced options
to see the corresponding text field).
This last step will ensure that your private key (which never left your
box) and the certificate belong together (through the public key that
will find its way into the certificate via the certificate-request).
You are now ready and can create your CAcert certified certificate.
Download and store or copy-and-paste it as
.Dq pub.crt .
.
.Pp
Yay.
In order to use your new S/MIME setup you will have to create
a combined private key/public key (certificate) file:
.
.Pp
.Dl cat key.pem pub.crt > ME@HERE.com.paired
.
.Pp
This is the file \*(UA will work with.
If you have created your private key with a passphrase then \*(UA will
ask you for it whenever a message is signed or decrypted.
Set the following variables to henceforth use S/MIME (setting
.Va smime-ca-file
is of interest for verification only):
.
.Bd -literal -offset indent
set smime-ca-file=ALL-TRUSTED-ROOT-CERTS-HERE \e
  smime-sign-cert=ME@HERE.com.paired \e
  smime-sign-message-digest=SHA256 \e
  smime-sign
.Ed
.
.Pp
From each signed message you send, the recipient can fetch your
certificate and use it to send encrypted mail back to you.
Accordingly if somebody sends you a signed message, you can do the same,
and use the
.Ic verify
command to check the validity of the certificate.
.
.Pp
Options of interest for S/MIME signing:
.Va smime-ca-dir ,
.Va smime-ca-file ,
.Va smime-crl-dir ,
.Va smime-crl-file ,
.Va smime-no-default-ca ,
.Va smime-sign ,
.Va smime-sign-cert ,
.Va smime-sign-include-certs
and
.Va smime-sign-message-digest .
.
.Pp
After it has been verified save the certificate via
.Ic certsave
and tell \*(UA that it should use it for encryption for further
communication with that somebody:
.
.Bd -literal -offset indent
certsave FILENAME
set smime-encrypt-USER@HOST=FILENAME \e
    smime-cipher-USER@HOST=AES256
.Ed
.
.Pp
Additional options of interest for S/MIME en- and decryption:
.Va smime-cipher
and
.Va smime-encrypt-USER@HOST .
.
.Pp
You should carefully consider if you prefer to store encrypted messages
in decrypted form.
If you do, anybody who has access to your mail folders can read them,
but if you do not, you might be unable to read them yourself later if
you happen to lose your private key.
The
.Ic decrypt
command saves messages in decrypted form, while the
.Ic save , copy ,
and
.Ic move
commands leave them encrypted.
.
.Pp
Note that neither S/MIME signing nor encryption applies to message
subjects or other header fields yet.
Thus they may not contain sensitive information for encrypted messages,
and cannot be trusted even if the message content has been verified.
When sending signed messages,
it is recommended to repeat any important header information in the
message text.
.\" }}}
.
.\" .Ss "Using CRLs with S/MIME or SSL/TLS" {{{
.Ss "Using CRLs with S/MIME or SSL/TLS"
.
\*(OP Certification authorities (CAs) issue certificate revocation
lists (CRLs) on a regular basis.
These lists contain the serial numbers of certificates that have been
declared invalid after they have been issued.
Such usually happens because the private key for the certificate has
been compromised,
because the owner of the certificate has left the organization that is
mentioned in the certificate, etc.
To seriously use S/MIME or SSL/TLS verification,
an up-to-date CRL is required for each trusted CA.
There is otherwise no method to distinguish between valid and
invalidated certificates.
\*(UA currently offers no mechanism to fetch CRLs, nor to access them on
the Internet, so you have to retrieve them by some external mechanism.
.
.Pp
\*(UA accepts CRLs in PEM format only;
CRLs in DER format must be converted, like, e.\|g.:
.
.Pp
.Dl $ openssl crl \-inform DER \-in crl.der \-out crl.pem
.
.Pp
To tell \*(UA about the CRLs, a directory that contains all CRL files
(and no other files) must be created.
The
.Va smime-crl-dir
or
.Va ssl-crl-dir
variables, respectively, must then be set to point to that directory.
After that, \*(UA requires a CRL to be present for each CA that is used
to verify a certificate.
.\" }}}
.
.\" .Ss "Handling spam" {{{
.Ss "Handling spam"
.
\*(OP \*(UA can make use of several spam interfaces for the purpose of
identification of, and, in general, dealing with spam messages.
A precondition of most commands in order to function is that the
.Va spam-interface
variable is set to one of the supported interfaces.
Once messages have been identified as spam their (volatile)
.Ql is-spam
state can be prompted: the
.Ql Ar :s
and
.Ql Ar :S
message specifications will address respective messages and their
.Va attrlist
entries will be used when displaying the
.Va headline
in the header display.
.
.Bl -bullet
.It
.Ic spamrate
rates the given messages and sets their
.Ql is-spam
flag accordingly.
If the spam interface offers spam scores those can also be displayed in
the header display by including the
.Ql %$
format in the
.Va headline
variable.
.It
.Ic spamham ,
.Ic spamspam
and
.Ic spamforget
will interact with the Bayesian filter of the chosen interface and learn
the given messages as
.Dq ham
or
.Dq spam ,
respectively; the last command can be used to cause
.Dq unlearning
of messages; it adheres to their current
.Ql is-spam
state and thus reverts previous teachings.
.It
.Ic spamclear
and
.Ic spamset
will simply set and clear, respectively, the mentioned volatile
.Ql is-spam
message flag, without any interface interaction.
.El
.
.Pp
The
.Xr spamassassin 1
based
.Va spam-interface Ns s
.Ql spamc
and
.Ql spamd
require a running instance of the
.Xr spamd 1
server in order to function, started with the option
.Fl -allow-tell
shall Bayesian filter learning be possible.
.Ql spamd
only works via a local path-based
.Xr unix 4
socket, but otherwise the following will be equivalently fine:
.
.Bd -literal -offset indent
$ spamd -i localhost:2142 -i /tmp/.spamsock -d [-L] [-l]
$ spamd --listen=localhost:2142 --listen=/tmp/.spamsock \e
    --daemonize [--local] [--allow-tell]
.Ed
.
.Pp
Thereafter \*(UA can make use of these interfaces:
.
.Bd -literal -offset indent
$ \*(ua -Sspam-interface=spamd -Sspam-maxsize=500000 \e
    -Sspamd-socket=/tmp/.spamsock -Sspamd-user=

$ \*(ua -Sspam-interface=spamc -Sspam-maxsize=500000 \e
    -Sspamc-command=/usr/local/bin/spamc \e
    -Sspamc-arguments="-U /tmp/.spamsock" -Sspamc-user=
or
$ \*(ua -Sspam-interface=spamc -Sspam-maxsize=500000 \e
    -Sspamc-command=/usr/local/bin/spamc \e
    -Sspamc-arguments="-d localhost -p 2142" -Sspamc-user=
.Ed
.
.Pp
Using the generic filter approach allows usage of programs like
.Xr bogofilter 1
and
.Xr sylfilter 1 .
Here is an example for the former, requiring it to be accessible via
.Ev PATH :
.
.Bd -literal -offset indent
$ \*(ua -Sspam-interface=filter -Sspam-maxsize=500000 \e
    -Sspamfilter-ham="bogofilter -n" \e
    -Sspamfilter-noham="bogofilter -N" \e
    -Sspamfilter-nospam="bogofilter -S" \e
    -Sspamfilter-rate="bogofilter -TTu 2>/dev/null" \e
    -Sspamfilter-spam="bogofilter -s" \e
    -Sspamfilter-rate-scanscore="1;^(.+)$"
.Ed
.
.Pp
Because messages must exist on local storage in order to be scored (or
used for Bayesian filter training), it is possibly a good idea to
perform the local spam check last:
.
.Bd -literal -offset indent
define spamdelhook {
  # Server side DCC
  spamset (header x-dcc-brand-metrics "bulk")
  # Server-side spamassassin(1)
  spamset (header x-spam-flag "YES")
  del :s # TODO we HAVE to be able to do `spamrate :u ! :sS'
  move :S +maybe-spam
  spamrate :u
  del :s
  move :S +maybe-spam
}
set folder-hook-FOLDER=spamdelhook
.Ed
.
.Pp
See also the documentation for the variables
.Va spam-interface , spam-maxsize ,
.Va spamc-command , spamc-arguments , spamc-user ,
.Va spamd-socket , spamd-user ,
.Va spamfilter-ham , spamfilter-noham , spamfilter-nospam , \
  spamfilter-rate
and
.Va spamfilter-rate-scanscore .
.\" }}}
.\" }}} (Examples)
.
.
.\" .Sh "FAQ" {{{
.Sh "FAQ"
.
.\" .Ss "\*(UA shortly hangs on startup" {{{
.Ss "\*(UA shortly hangs on startup"
.
This can have two reasons, one is the necessity to wait for a file lock
and can't be helped, the other being that \*(UA calls the function
.Xr uname 2
in order to query the nodename of the box (sometimes the real one is
needed instead of the one represented by the internal variable
.Va hostname ) .
You may have varying success by ensuring that the real hostname and
.Ql localhost
have entries in
.Pa /etc/hosts ,
or, more generally, that the name service is properly setup \(en
and does
.Xr hostname 1
return what you'd expect?
.\" }}}
.
.\" .Ss "I can't login to Google mail a.k.a. GMail" {{{
.Ss "I can't login to Google mail a.k.a. GMail"
.
Since 2014 some free service providers classify programs as
.Dq less secure
unless they use a special authentification method (OAuth 2.0) which
wasn't standardized for non-HTTP protocol authentication token query
until August 2015 (RFC 7628).
.
.Pp
Different to Kerberos / GSSAPI, which is developed since the mid of the
1980s, where a user can easily create a local authentication ticket for
her- and himself with the locally installed
.Xr kinit 1
program, that protocol has no such local part but instead requires
a world-wide-web query to create or fetch a token; since there is no
local cache this query has to be performed whenever \*(UA is invoked
from the command line (in interactive sessions situation may differ).
.
.Pp
\*(UA doesn't support OAuth.
Because of this it is necessary to declare \*(UA a
.Dq less secure app
(on the providers account web page) in order to read and send mail.
However, it also seems possible to take the following steps instead:
.
.Pp
.Bl -enum -compact
.It
give the provider the number of a mobile phone,
.It
enable
.Dq 2-Step Verification ,
.It
create an application specific password (16 characters), and
.It
use that special password instead of your real Google account password in
S-nail (for more on that see the section
.Sx "On URL syntax and credential lookup" ) .
.El
.\" }}}
.\" }}}
.
.
.\" .Sh "SEE ALSO" {{{
.Sh "SEE ALSO"
.
.Xr bogofilter 1 ,
.Xr bzip2 1 ,
.Xr file 1 ,
.Xr fmt 1 ,
.Xr gpg 1 ,
.Xr gpg-agent 1 ,
.Xr gzip 1 ,
.Xr less 1 ,
.Xr more 1 ,
.Xr newaliases 1 ,
.Xr openssl 1 ,
.Xr postfix 1 ,
.Xr printf 1 ,
.Xr sendmail 1 ,
.Xr sh 1 ,
.Xr spamassassin 1 ,
.Xr spamc 1 ,
.Xr spamd 1 ,
.Xr sylfilter 1 ,
.Xr vacation 1 ,
.Xr xterm 1 ,
.Xr xz 1 ,
.Xr editline 3 ,
.Xr iconv 3 ,
.Xr readline 3 ,
.Xr setlocale 3 ,
.Xr ssl 3 ,
.Xr aliases 5 ,
.Xr locale 7 ,
.Xr mailaddr 7 ,
.Xr re_format 7 ,
.Xr exim 8 ,
.Xr mailwrapper 8 ,
.Xr sendmail 8
.\" }}}
.
.
.\" .Sh HISTORY {{{
.Sh HISTORY
.
A
.Em mail
command appeared in Version 1 AT&T Unix.
Berkeley Mail was written in 1978 by Kurt Shoens.
This man page is derived from from
.Dq The Mail Reference Manual
originally written by Kurt Shoens.
.Dq Heirloom Mailx
enhancements are maintained and documented by Gunnar
Ritter.
.Dq S-nail
is maintained and documented by Steffen (Daode) Nurpmeso.
.
.Pp
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
\(en Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright \(co 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original
IEEE and The Open Group Standard, the original IEEE and The Open Group
Standard is the referee document.
The original Standard can be obtained online at
.Lk http://www.opengroup.org/unix/online.html OpenGroup.org
Redistribution of this material is permitted so long as this notice
remains intact.
.\" }}}
.
.
.Sh AUTHORS
.
.An "Kurt Shoens" ,
.An "Christos Zoulas" ,
.An "Gunnar Ritter" ,
.An "Steffen Nurpmeso" Aq Mt s-nail-users@lists.sourceforge.net
(later
.Mt s-mailx@sdaoden.eu ) .
.
.
.\" .Sh CAVEATS {{{
.Sh CAVEATS
.
The character set conversion uses and relies upon the
.Xr iconv 3
function.
Its functionality differs widely between the various system environments
\*(UA runs on.
.
.Pp
Limitations with IMAP mailboxes are:
It is not possible to edit messages, but it is possible to append them.
Thus to edit a message, create a local copy of it, edit it, append it,
and delete the original.
The line count for the header display is only appropriate if the entire
message has been downloaded from the server.
The marking of messages as `new' is performed by the IMAP server;
use of the
.Ic exit
command instead of
.Ic quit
will not cause it to be reset, and if the
.Va newmail
variable is unset, messages that arrived during a session will not be
in state `new' anymore when the folder is opened again.
Also if commands queued in disconnected mode are committed,
the IMAP server will delete the `new' flag for all messages in the
changed folder,
and new messages will appear as unread when it is selected for viewing
later.
The `flagged', `answered', and `draft' attributes are usually permanent,
but some IMAP servers are known to drop them without notification.
Message numbers may change with IMAP every time before the prompt is
printed if \*(UA is notified by the server that messages have been
deleted by some other client or process.
In this case, `Expunged n messages' is printed, and message numbers may
have changed.
.
.Pp
Limitations with POP3 mailboxes are:
It is not possible to edit messages, they can only be copied and deleted.
The line count for the header display is only appropriate if the entire
message has been downloaded from the server.
The status field of a message is maintained by the server between
connections; some servers do not update it at all, and with a server
that does, the
.Ic exit
command will not cause the message status to be reset.
The
.Ic newmail
command and the
.Va newmail
variable have no effect.
It is not possible to rename or to remove POP3 mailboxes.
.
.Pp
If a
.Dq RUBOUT
(interrupt,
.Ql control-C )
is typed while an IMAP or POP3 operation is in progress, \*(UA will wait
until the operation can be safely aborted, and will then return to the
command loop and print the prompt again.
When a second
.Dq RUBOUT
is typed while \*(UA is waiting for the operation to complete, the
operation itself will be cancelled.
In this case, data that has not been fetched yet will have to be fetched
before the next command can be performed.
If the cancelled operation was using an SSL/TLS encrypted channel,
an error in the SSL transport will very likely result and render the
connection unusable.
.
.Pp
As \*(UA is a mail user agent, it provides only basic SMTP services.
If it fails to contact its upstream SMTP server, it will not make
further attempts to transfer the message at a later time,
and it does not leave other information about this condition than an
error message on the terminal and an entry in
.Ev DEAD .
This is usually not a problem if the SMTP server is located in the same
local network as the computer on which \*(UA is run.
However, care should be taken when using a remote server of an ISP;
it might be better to set up a local SMTP server then which just acts as
a proxy.
.
.Pp
\*(UA immediately contacts the SMTP server (or
.Xr sendmail 1 Ns
) even when operating in
.Va disconnected
mode.
It would not make much sense for \*(UA to defer outgoing mail since SMTP
servers usually provide much more elaborated delay handling than \*(UA
could perform as a client.
Thus the recommended setup for sending mail in
.Va disconnected
mode is to configure a local SMTP server such that it sends outgoing
mail as soon as an external network connection is available again,
i.e., to advise it to do that from a network startup script.
.\" }}}
.
.
.Sh BUGS
.
IMAP support is very basic, and doesn't support international mailbox
names as specified in RFC 3501.
Interrupting an IMAP operation can lead to endless iterations of the
same operation.
With IMAP, at least if the IMAP cache is used, if multiple
.Ic connect
and
.Ic disconnect
cycles happen without an intervening change of the active mailbox then
\*(UA will at some time loose the ability to keep the local state
up-to-date, meaning that, e.g., messages show up with false numbers, and
including the possibility that messages are accessed via numbers that
are no(t longer) valid, resulting in program crashes.
The solution is to change the active mailbox before that happens :).
Also see the file
.Pa TODO
from the distribution or the repository.
.
After deleting some message of a POP3 mailbox the header summary falsely
claims that there are no messages to display, you need to perform
a scroll or dot movement to restore proper state.
.
In threaded display a power user may encounter crashes very
occasionally (this is may and very).
.\" s-ts-mode