*m*ail and *M*ail support all recipients! Use lextract()

[s-mailx.git] / nail.1

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.\"     The Regents of the University of California.  All rights reserved.
.\" Copyright (c) 2000
.\"     Gunnar Ritter.  All rights reserved.
.\" Copyright (c) 2012 Steffen "Daode" Nurpmeso.
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.\"--MKMAN-START--
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.ds UA \\fIS-nail\\fR
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.\"--MKMAN-END--
.\" If not ~/.mailrc, it breaks POSIX compatibility.  And adjust main.c.
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.\"
.\" ##  --  >8  --  8<  --  ##
.\"
.TH "\*(UU" 1 "2012-10-05" "\*(uu" "User Commands"
.SH NAME
\*(UA \- send and receive Internet mail
.SH SYNOPSIS
.PD 0
.HP
.ad l
\*(ba [\fB\-BDdEFintv~\fR]
[\fB\-A\fI\ account\fR]
[\fB\-a\fI\ attachment\fR]
[\fB\-b\fI\ bcc-addr\fR] [\fB\-c\fI\ cc-addr\fR]
[\fB\-O\fI\ mta-option [\fB\-O\fI mta-option-argument]\fR]
[\fB\-q\fI\ quote-file\fR]
[\fB\-r\fI\ from-addr\fR]
[\fB\-S\fI\ variable\fR[\fB=\fIvalue\fR]]
[\fB\-s\fI\ subject\fR]
\fIto-addr\fR .\ .\ .
.HP
.ad l
\*(ba [\fB\-BDdEeHIiNnRv~\fR]
[\fB\-A\fI\ account\fR]
[\fB\-S\fI\ variable\fR[\fB=\fIvalue\fR]]
[\fB\-T\fI\ name\fR]
\fB\-f\fR [\fIfile\fR]
.HP
.ad l
\*(ba [\fB\-BDdEeiNnRv~\fR]
[\fB\-A\fI\ account\fR]
[\fB\-S\fI\ variable\fR[\fB=\fIvalue\fR]]
[\fB\-u\fI\ user\fR]
.br
.PD
.ad b
.SH DESCRIPTION
\*(UA is an intelligent mail processing system, which has a command syntax
reminiscent of
.IR ed (1)
with lines replaced by messages.
It is based on Heirloom mailx, that is based on Berkeley Mail 8.1,
is intended to provide the functionality of the POSIX
.B mailx
command,
and offers extensions for IDNA, MIME, IMAP, POP3, SMTP, and S/MIME.
\*(UA provides enhanced features for interactive use, such as caching
and disconnected operation for IMAP, message threading, scoring, and
filtering.
It is also usable as a mail batch language, both for sending and
receiving mail.
.PP
The following options are accepted:
.\"
.TP
.BI \-A \ name
Executes an 
.I account
command (see below) for \fIname\fR after the startup files have been
read.
.TP
.BI \-a \ file
Attach the given file to the message.
.TP
.B \-B
Make standard input and standard output line-buffered.
.TP
.BI \-b \ address
Send blind carbon copies to the given list of addresses.
\fISending mail\fR below goes into more detail on that.
.TP
.BI \-c \ address
Send carbon copies to the given list of addresses.
.TP
.B \-D
Start in
.I disconnected
mode; see the description for the
.I disconnected
variable option.
.TP
.B \-d
Enables debugging messages and disables the actual delivery of messages.
Unlike
.IR \-v ,
this option is intended for \*(UA development only.
.TP
.B \-E
If an outgoing message does not contain any text in its first or only
message part, do not send but discard it silently,
effectively setting the
.I skipemptybody
variable at program startup.
This is useful for sending messages from scripts started by
.IR cron (8).
.TP
.B \-e
Just check if mail is present in the system mailbox.
If yes, return an exit status of zero, a non-zero value otherwise.
.TP
.B \-F
Save the message to send in a file named after the local part of the
first recipient's address.
.TP
\fB\-f\fR [\fIfile\fR]
Read in the contents of the user's mbox (or the specified file)
for processing;
when \*(UA is quit, it writes undeleted messages back to this file.
The string \fIfile\fR is handled as described for the
.I folder
command below.
Note that \fIfile\fR is not a direct argument to the \fB-f\fR option,
but instead taken from the command line after option processing has been
completed.
.TP
.B \-H
Print header summaries for all messages and exit.
.TP
.B \-I
Shows the `Newsgroup:' or `Article-Id:' fields in the header summary.
Only applicable in combination with
.IR \-f .
.TP
.B \-i
Ignore tty interrupt signals.
This is particularly useful when using \*(UA on noisy phone lines.
.TP
.B \-N
Inhibits the initial display of message headers when reading mail
or editing a mail folder.
.TP
.B \-n
Inhibits reading \*(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.
.TP
.BI \-O \ option
Pass the given option through to the mail-transfer-agent (MTA).
This option has no effect when SMTP is used for sending mail.
E.g., to specify the hop count to an old \fIsendmail(1)\fR, use
`\fI-O-h -Onumber\fR', which will be passed as `\fI-h number\fR'.
.TP
.BI \-q \ file
Start the message with the contents of the specified file.
May be given in send mode only.
.TP
.B \-R
Opens any folders read-only.
.TP
.BI \-r \ address
Sets the
.I From
address. Overrides any
.I from
variable specified in environment or startup files.
Tilde escapes are disabled.
The \fI\-r\fI address\fR options are passed to the mail transfer agent
unless SMTP is used.
This option exists for compatibility only; it is recommended to set the
.I from
variable directly instead.
.TP
\fB\-S\fI\ variable\fR[\fB=\fIvalue\fR]
Sets the internal option
.I variable
and, in case of a string option, assigns \fIvalue\fR to it.
These assignments become active immediately,
but also cannot be overwritten by resource file content.
.TP
.BI \-s \ subject
Specify subject on command line (only the first argument after the
.I \-s
flag is used as a subject; be careful to quote subjects containing spaces).
.TP
.BI \-T \ name
Writes the `Message-Id:' and `Article-Id:' header fields of each message
read in the file
.IR name .
Implies
.IR \-I .
Compressed files are handled as described for the \fIfolder\fR command
below.
.TP
.B \-t
The message to be sent is expected to contain a message header with
`To:', `Cc:', or `Bcc:' fields giving its recipients and `Subject:'
giving the subject of the message.
Recipients and subject specified on the command line are ignored.
.TP
.BI \-u \ user
Reads the mailbox of the given user name.
.TP
.B \-V
Print \*(UA's version and exit.
.TP
.B \-v
Verbose mode.
The details of delivery are displayed on the user's terminal.
.TP
.B \-~
Enable tilde escapes even if not in interactive mode.
.\"
.SS "Sending mail"
To send a message to one or more people, \*(UA can be invoked with
arguments which are the names of people to whom the mail will be sent.
These names may be \fIalias\fRes, plain addresses or full address
specifications including user names and comments, in which case care
for proper quoting may be necessary.
The section \fIRecipient address specifications\fR below explains the
interpretation of addresses in more detail.
The user is then expected to type in his message, followed by an
`control-D' at the beginning of a line.
The section \fIReplying to or originating mail\fI, describes some
features of \*(UA available to help when composing letters.
.SS "Reading mail"
In normal usage \*(UA is given no arguments and checks the user's mail
out of the post office, then prints out a one line header of each
message found.
The current message is initially the first message (numbered 1) and can
be printed using the print command which can be abbreviated `p').
The user can move among the messages much as he moves between lines in
.IR ed (1),
with the commands `+' and `\-' moving backwards and forwards,
and simple numbers.
.SS "Disposing of mail"
After examining a message the user can delete `d') the message or reply
`r') to it.
Deletion causes the \*(UA program to forget about the message.
This is not irreversible;
the message can be undeleted `u') by giving its number,
or the \*(UA session can be aborted by giving the exit `x') command.
Deleted messages will, however, usually disappear never to be seen
again.
.SS "Specifying messages"
Commands such as print and delete can be given a list of message numbers
as arguments to apply to a number of messages at once.
Thus `\fIdelete 1 2\fR' deletes messages 1 and 2, while
`\fIdelete 1-5\fR' deletes messages 1 through 5.
In sorted or threaded mode (see the
.I sort
and
.I thread
commands),
`\fIdelete 1-5\fR' deletes the messages that are located between (and
including) messages 1 through 5 in the sorted/threaded order, as shown
in the header summary.
The following special message names exist:
.TP
.B :n
All new messages.
.TP
.B :o
All old messages (any not in state read or new).
.TP
.B :u
All unread messages.
.TP
.B :d
All deleted messages (for the
.I undelete
command).
.TP
.B :r
All read messages.
.TP
.B :f
All `flagged' messages.
.TP
.B :a
All answered messages
(cf. the
.I markanswered
variable).
.TP
.B :t
All messages marked as draft.
.TP
.B :k
All `killed' messages.
.TP
.B :j
All messages classified as junk.
.TP
.B .
The current message.
.TP
.B ;
The message that was previously the current message.
.TP
.B ,
The parent message of the current message,
that is the message with the Message-ID
given in the `In-Reply-To:' field
or the last entry of the `References:' field
of the current message.
.TP
.B \-
The next previous undeleted message,
or the next previous deleted message for the
.I undelete
command.
In sorted/threaded mode,
the next previous such message in the sorted/threaded order.
.TP
.B +
The next undeleted message,
or the next deleted message for the
.I undelete
command.
In sorted/threaded mode,
the next such message in the sorted/threaded order.
.TP
.B ^
The first undeleted message,
or the first deleted message
for the
.I undelete
command.
In sorted/threaded mode,
the first such message in the sorted/threaded order.
.TP
.B $
The last message.
In sorted/threaded mode,
the last message in the sorted/threaded order.
.TP
.BI & x
In threaded mode,
selects the message addressed with
.IR x ,
where
.I x
is any other message specification,
and all messages from the thread that begins at it.
Otherwise, it is identical to
.IR x .
If
.I x
is omitted,
the thread beginning with the current message is selected.
.TP
.B *
All messages.
.TP
.B `
All messages that were included in the message list
for the previous command.
.TP
.BI / string
All messages that contain
.I string
in the subject field (case ignored).
See also the
.I searchheaders
variable.
If
.I string
is empty,
the string from the previous specification of that type is used again.
.TP
.I address
All messages from
.IR address .
By default, this is a case-sensitive search
for the complete email address.
If the
.I allnet
variable is set,
only the local part of the addresses is evaluated for the comparison.
Otherwise if the
.I showname
variable is set,
a case-sensitive search for the complete real name
of a sender is performed.
The IMAP-style
.BI (from\  address)
expression can be used instead
if substring matches are desired.
.TP
.BI ( criterion )
All messages that satisfy the given IMAP-style SEARCH
.IR criterion .
This addressing mode is available with all types of folders;
for folders not located on IMAP servers,
or for servers unable to execute the SEARCH command,
\*(UA will perform the search locally.
Strings must be enclosed by double quotes `"' in their entirety
if they contain white space or parentheses;
within the quotes,
only backslash `\e' is recognized as an escape character.
All string searches are case-insensitive.
When the description indicates
that the `envelope' representation of an address field is used,
this means that the search string is checked against
both a list constructed as
.nf
.sp
\fB("\fIreal name\fB" "\fIsource-route\fB" "\fIlocal-part\fB" "\fIdomain-part\fB")\fR
.sp
.fi
for each address,
and the addresses without real names
from the respective header field.
Criteria can be nested using parentheses.
.TP
\fB(\fIcriterion1 criterion2\fR .\|.\|. \fIcriterionN\fB)\fR
All messages that satisfy all of the given criteria.
.TP
.BI (or " criterion1 criterion2" )
All messages that satisfy either
.I criterion1
or
.IR criterion2 ,
or both.
To connect more than two criteria using `or',
(or) specifications have to be nested using additional parentheses,
as with `(or\ a\ (or\ b\ c))';
`(or\ a\ b\ c)' means ((a or b) and c).
For a simple `or' operation of independent criteria
on the lowest nesting level,
it is possible to achieve similar effects by using
three separate criteria, as with
`(a)\ (b)\ (c)'.
.TP
.BI (not " criterion" )
All messages that do not satisfy
.IR criterion .
.TP
.BI (bcc " string" )
All messages that contain
.I string
in the `envelope' representation of the
.I Bcc:
field.
.TP
.BI (cc " string" )
All messages that contain
.I string
in the `envelope' representation of the
.I Cc:
field.
.TP
.BI (from " string" )
All messages that contain
.I string
in the `envelope' representation of the
.I From:
field.
.TP
.BI (subject " string" )
All messages that contain
.I string
in the
.I Subject:
field.
.TP
.BI (to " string" )
All messages that contain
.I string
in the `envelope' representation of the
.I To:
field.
.TP
.BI (header " name string" )
All messages that contain
.I string
in the specified
.I Name:
field.
.TP
.BI (body " string" )
All messages that contain
.I string
in their body.
.TP
.BI (text " string" )
All messages that contain
.I string
in their header or body.
.TP
.BI (larger " size" )
All messages that are larger than
.I size
(in bytes).
.TP
.BI (smaller " size" )
All messages that are smaller than
.I size
(in bytes).
.TP
.BI (before " date" )
All messages that were received before
.IR date ;
.I date
must be in the form
\fId\fR[\fId\fR]\fB-\fImon\fB-\fIyyyy\fR,
where \fId\fR[\fId\fR] is the day of the month
as one or two digits,
.I mon
is the name of the month\(emone of
`Jan', `Feb', `Mar',
`Apr', `May', `Jun',
`Jul', `Aug', `Sep',
`Oct', `Nov', or `Dec',
and
.I yyyy
is the year as four digits;
e.\|g. "30-Aug-2004".
.TP
.BI (on " date" )
All messages that were received on the specified date.
.TP
.BI (since " date" )
All messages that were received since the specified date.
.TP
.BI (sentbefore " date" )
All messages that were sent on the specified date.
.TP
.BI (senton " date" )
All messages that were sent on the specified date.
.TP
.BI (sentsince " date" )
All messages that were sent since the specified date.
.TP
.B ()
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,
the last of those criteria is used.
.PP
A practical method to read a set of messages
is to issue a
.I from
command with the search criteria first
to check for appropriate messages,
and to read each single message then by typing `\fB`\fR' repeatedly.
.SS "Replying to or originating mail"
The
.I reply
command can be used
to set up a response to a message,
sending it back to the person who it was from.
Text the user types in then,
up to an end-of-file,
defines the contents of the message.
While the user is composing a message,
\*(UA treats lines beginning with the character `~' specially.
For instance, typing `~m' (alone on a line)
will place a copy of the current message into the response
right shifting it by a tabstop
(see
.I indentprefix
variable, below).
Other escapes will set up subject fields,
add and delete recipients to the message,
attach files to it
and allow the user to escape to an editor
to revise the message
or to a shell to run some commands.
(These options are given in the summary below.)
.SS "Ending a mail processing session"
The user can end a \*(UA session
with the quit (`q') command.
Messages which have been examined
go to the user's mbox file
unless they have been deleted
in which case they are discarded.
Unexamined messages go back
to the post office.
(See the \-f option above).
.SS "Personal and systemwide distribution lists"
It is also possible to create
a personal distribution lists so that,
for instance, the user can send mail
to `\fIcohorts\fR' and have it go
to a group of people.
Such lists can be defined by placing a line like
.nf

        \fBalias\fI cohorts bill ozalp jkf mark kridle@ucbcory\fR

.fi
in the file \*(ur in the user's home directory.
The currently defined list of such aliases can be displayed with the alias
command in \*(UA.
System wide distribution lists can be created by editing /etc/aliases, see
\fIaliases(5)\fR and \fIsendmail(1)\fR;
these are kept in a different syntax and are used by the MTA, not \*(UA.
In mail the user sends, personal aliases will be expanded in mail sent to
others so that they will be able to reply to the recipients.
System wide aliases are not expanded when the mail is sent,
but any reply returned to the machine will have the system wide alias
expanded as all mail goes through \fIsendmail(1)\fR.
.SS "Recipient address specifications"
When an address is used to name a recipient
(in any of To, Cc, or Bcc),
names of local mail folders
and pipes to external commands
can also be specified;
the message text is then written to them.
The rules are: Any name which starts with a
.RB ` | '
character specifies a pipe,
the command string following the `|'
is executed and the message is sent to its standard input;
any other name which contains a
.RB ` @ '
character is treated as a mail address;
any other name which starts with a
.RB ` + '
character specifies a folder name;
any other name which contains a
.RB ` / '
character
but no
.RB ` ! '
or
.RB ` % '
character before also specifies a folder name;
what remains is treated as a mail address.
Compressed folders are handled as described for the
.I folder
command below.
.SS "Network mail (Internet / ARPA, UUCP, Berknet)"
See
.IR mailaddr (7)
for a description of network addresses.
\*(UA has a number of options which can be set in the \*(ur file
to alter its behavior;
thus `\fIset askcc\fR' enables the askcc feature.
(These options are summarized below).
.SS "MIME types"
For any outgoing attachment,
\*(UA tries to determine the content type.
It does this by reading MIME type files
whose lines have the following syntax:
.nf

        \fItype\fB/\fIsubtype      extension \fR[\fIextension \fR.\ .\ .]\fR

.fi
where type/subtype are strings describing the file contents,
and extension is the part of a filename starting after the last dot.
Any line not immediately beginning with an ASCII alphabetical character is
ignored by \*(UA.
If there is a match with the extension of the file to attach,
the given type/subtype pair is used.
Otherwise, or if the filename has no extension,
the content types text/plain or application/octet-stream are used,
the first for text or international text files,
the second for any file that contains formatting characters
other than newlines and horizontal tabulators.
.SS "Character sets"
\*(UA normally detects the character set of the terminal
using the LC_CTYPE locale setting.
If the locale cannot be used appropriately,
the \fIttycharset\fR variable should be set
to provide an explicit value.
When reading messages,
their text is converted to the terminal character set if possible.
Unprintable characters and illegal byte sequences are detected
and replaced by Unicode substitute characters or question marks
unless the
.I print-all-chars
is set at initialization time.
.PP
The character set for outgoing messages
is not necessarily the same
as the one used on the terminal.
If an outgoing text message
contains characters not representable in US-ASCII,
the character set being used
must be declared within its header.
Permissible values can be declared
using the \fIsendcharsets\fR variable,
separated by commas;
\*(UA tries each of the values in order
and uses the first appropriate one.
If the message contains characters that cannot be represented
in any of the given character sets,
the message will not be sent,
and its text will be saved to the `dead.letter' file.
Messages that contain NUL bytes are not converted.
.PP
Outgoing attachments are converted if they are plain text.
If the
.I sendcharsets
variable contains more than one character set name,
the
.I ~@
tilde escape will ask for the character sets for individual attachments
if it is invoked without arguments.
.PP
Best results are usually achieved
when \*(UA is run in a UTF-8 locale
on a UTF-8 capable terminal.
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 "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.
For commands which take message lists as arguments,
if no message list is given,
then the next message forward which satisfies
the command's requirements is used.
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 `\fIapplicable messages\fR' and aborts the command.
If the command begins with a \fI#\fR sign,
the line is ignored.
.PP
The arguments to commands can be quoted, using the following methods:
.IP \(bu
An argument can be enclosed between paired double-quotes
"\|" or single-quotes '\|'; any white space, shell
word expansion, or backslash characters within the quotes
are treated literally as part of the argument.
A double-quote will be treated literally within
single-quotes and vice versa. These special properties of
the quote marks occur only when they are paired at the
beginning and end of the argument.
.IP \(bu
A backslash outside of the enclosing quotes is discarded
and the following character is treated literally as part of
the argument.
.IP \(bu
An unquoted backslash at the end of a command line is
discarded and the next line continues the command.
.PP
Filenames, where expected, are subjected to the following
transformations, in sequence:
.IP \(bu
If the filename begins with an unquoted plus sign, and
the
.I folder
variable is defined,
the plus sign will be replaced by the value of the
.I folder
variable followed by a slash. If the
.I folder
variable is
unset or is set to null, the filename will be unchanged.
.IP \(bu
Shell word expansions are applied to the filename.
If more than a single pathname results
from this expansion and the command is expecting one
file, an error results.
.PP
The following commands are provided:
.TP
.B \-
Print out the preceding message.
If given a numeric argument n,
goes to the n'th previous message and prints it.
.TP
.B ?
Prints a brief summary of commands.
.TP
.B !
Executes the shell (see
.IR sh (1)
and
.IR csh (1))
command which follows.
.TP
.B |
A synonym for the \fIpipe\fR command.
.TP
.B account
(ac) Creates, selects or lists
an email account.
An account is formed by a group of commands,
primarily of those to set variables.
With two arguments,
of which the second is a `{',
the first argument gives an account name,
and the following lines create a group of commands for that account
until a line containing a single `}' appears.
With one argument,
the previously created group of commands
for the account name is executed,
and a
.I folder
command is executed for the system mailbox or inbox
of that account.
Without arguments,
the list of accounts and their contents are printed.
As an example,
.sp
.nf
    \fBaccount\fI myisp\fR \fB{\fR
        set folder=imaps://mylogin@imap.myisp.example
        set record=+Sent
        set from="myname@myisp.example (My Name)"
        set smtp=smtp.myisp.example
    \fB}\fR
.fi
.sp
creates an account named `myisp'
which can later be selected by specifying `account myisp'.
.TP
.B 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 changes an old one.
.TP
.B alternates
(alt) The alternates command is useful
if the user has accounts on several machines.
It can be used to inform \*(UA
that the listed addresses all belong to the invoking user.
When he replies to messages,
\*(UA will not send a copy of the message
to any of the addresses
listed on the alternates list.
If the alternates command is given
with no argument,
the current set of alternate names is displayed.
.TP
.B answered
(ans) Takes a message list and marks each message
as a 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.
.TP
.B cache
Only applicable to cached IMAP mailboxes;
takes a message list and reads the specified messages
into the IMAP cache.
.TP
.B call
Calls a macro (see the
.I define
command).
.TP
.B cd
Same as chdir.
.TP
.B certsave
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 messages' originators by setting the
.I smime-encrypt-user@host
variable.
.TP
.B chdir
(ch) Changes the user's working directory to that specified,
if given.
If no directory is given,
then changes to the user's login directory.
.TP
.B classify
(cl) Takes a list of messages and
examines their contents for characteristics of junk mail
using Bayesian filtering.
Messages considered to be junk are then marked as such.
The junk mail database is not changed.
.TP
.B collapse
(coll)
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 `new'.
.TP
.B connect
(conn) 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
.I disconnected
variable for more information.
.TP
.B copy
(c) The copy command does the same thing that
.I save
does,
except that it does not mark the messages
it is used on for deletion when the user quits.
Compressed files and IMAP mailboxes are handled as described for the
.I folder
command.
.TP
.B Copy
(C) Similar to
.IR copy ,
but saves the messages in a file named after the local part
of the sender address of the first message.
.TP
.B decrypt
(dec) For unencrypted messages,
this command is identical to
.IR copy .
Encrypted messages are first decrypted, if possible,
and then copied.
.TP
.B Decrypt
(Dec) Similar to
.IR decrypt ,
but saves the messages in a file named after the local part
of the sender address of the first message.
.TP
.B define
(def) Defines a macro.
A macro definition is a sequence of commands in the following form:
.sp
.nf
    \fBdefine\fR \fIname\fB {\fR
        \fIcommand1\fR
        \fIcommand2\fR
        .\|.\|.
        \fIcommandN\fR
    \fB}\fR
.fi
.sp
Once defined, a macro can be explicitly invoked using the
.I call
command,
or can be implicitly invoked by setting the
.I folder-hook
or
.I folder-hook-fullname
variables.
.TP
.B defines
Prints the currently defined macros including their contents.
.TP
.B delete
(d) Takes a list of messages as argument
and marks them all as deleted.
Deleted messages will not be saved in mbox,
nor will they be available for most other commands.
.TP
.B discard
Same as ignore.
.TP
.B disconnect
(disco) If operating in online mode on an IMAP mailbox,
switch to disconnected mode while retaining the mailbox status.
See the description of the
.I disconnected
variable for more information.
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 current mailbox
available for disconnected use.
.TP
.BR dp \ or \ dt
Deletes the current message
and prints the next message.
If there is no next message,
\*(UA says `\fIat EOF\fR'.
.TP
.B draft
Takes a message list and marks each 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.
.TP
.B echo
Echoes its arguments,
resolving special names
as documented for the folder command.
The escape sequences
`\fB\ea\fR',
`\fB\eb\fR',
`\fB\ec\fR',
`\fB\ef\fR',
`\fB\en\fR',
`\fB\er\fR',
`\fB\et\fR',
`\fB\ev\fR',
`\fB\e\e\fR', and
`\fB\e0\fInum\fR'
are interpreted
as with the
.IR echo (1)
command.
.TP
.B edit
(e) Takes a list of messages
and points the text editor
at each one in turn.
Modified contents are discarded
unless the
.I writebackedited
variable is set.
.TP
.B else
Marks the end of the then-part
of an if statement
and the beginning of the part
to take effect if the condition
of the if statement is false.
.TP
.B endif
Marks the end of an if statement.
.TP
.B exit
(ex or x) Effects an immediate return to the Shell
without modifying the user's system mailbox,
his mbox file,
or his edit file in \-f.
.TP
.B file
(fi) The same as folder.
.TP
.B flag
(fl) Takes a message list
and marks the messages as `flagged' 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.
.TP
.B folders
With no arguments,
list the names of the folders in the folder directory.
With an existing folder as an argument,
lists then 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
.I imap-list-depth
variable.
.TP
.B folder
(fold) The folder command switches
to a new mail file or folder.
With no arguments, it tells the user
which file he is currently reading.
If an argument is given,
it will write out changes
(such as deletions) the user has made
in the current file and read in
the new file.
Some special conventions are recognized for the name.
\fB#\fR means the previous file,
\fB%\fR means the invoking user's system mailbox,
\fB%\fIuser\fR means \fIuser's\fR system mailbox,
\fB&\fR means the invoking user's mbox file,
and \fB+\fIfile\fI means a \fIfile\fR in the folder directory.
\fB%:\fIfilespec\fR expands to the same value as \fIfilespec\fR,
but the file is handled as a system mailbox
e.\ g. by the mbox and save commands.
If the name matches one of the strings defined with the
.I shortcut
command,
it is replaced by its long form and expanded.
If the name ends with \fB.gz\fR or \fB.bz2\fR,
it is treated as compressed with
.IR gzip (1)
or
.IR bzip2 (1),
respectively.
Likewise, if \fIname\fR does not exist,
but either \fIname\fB.gz\fR or \fIname\fB.bz2\fR exists,
the compressed file is used.
If \fIname\fR refers to a directory
with the subdirectories `tmp', `new', and `cur',
it is treated as a folder in
.I maildir
format.
A name of the form
.nf

       \fIprotocol\fB://\fR[\fIuser\fB@\fR]\fIhost\fR[\fB:\fIport\fR][\fB/\fIfile\fR]

.fi
is taken as an Internet mailbox specification.
The supported protocols are currently
.B imap
(IMAP v4r1),
.B imaps
(IMAP with SSL/TLS encryption),
.B pop3
(POP3),
and
.B pop3s
(POP3 with SSL/TLS encryption).
If
.I user
contains special characters, in particular `/' or `%',
they must be escaped in URL notation,
as `%2F' or `%25'.
The optional
.I file
part applies to IMAP only;
if it is omitted,
the default `INBOX' is used.
If \*(UA is connected to an IMAP server,
a name of the form \fB@\fImailbox\fR
refers to the \fImailbox\fR on that server.
If the `folder' variable refers to an IMAP account,
the special name `%' selects the `INBOX' on that account.
.TP
.B Followup
(F) Similar to
.IR Respond ,
but saves the message in a file
named after the local part of the first recipient's address.
.TP
.B followup
(fo) Similar to
.IR respond ,
but saves the message in a file
named after the local part of the first recipient's address.
.TP
.B followupall
Similar to
.IR followup ,
but responds to all recipients regardless of the
.I flipr
and
.I Replyall
variables.
.TP
.B followupsender
Similar to
.IR Followup ,
but responds to the sender only regardless of the
.I flipr
and
.I Replyall
variables.
.TP
.B forward
(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
.I fwdheading
variable printed before.
The
.I fwdignore
and
.I fwdretain
commands specify which header fields are included in the new message.
Only the first part of a multipart message is included unless the
.I forward-as-attachment
option is set.
.TP
.B Forward
(Fwd)
Similar to
.IR forward ,
but saves the message in a file named after
the local part of the recipient's address.
.TP
.B from
(f) Takes a list of messages
and prints their message headers,
piped through the pager if the output does not fit on the screen.
.TP
.B fwdignore
Specifies which header fields are to be ignored with the
.I forward
command.
This command has no effect when the
.I forward-as-attachment
option is set.
.TP
.B fwdretain
Specifies which header fields are to be retained with the
.I forward
command.
.I fwdretain
overrides
.IR fwdignore .
This command has no effect when the
.I forward-as-attachment
option is set.
.TP
.B good
(go) Takes a list of messages
and marks all of them as not being junk mail.
Data from these messages is then inserted
into the junk mail database for future classification.
.TP
.B headers
(h) Lists the current range of headers,
which is an 18-message group.
If a `+' argument is given,
then the next 18-message group is printed,
and if a `\-' argument is given,
the previous 18-message group is printed.
.TP
.B help
A synonym for ?.
.TP
.B hold
(ho, also preserve) Takes a message list
and marks each message therein to be saved
in the user's system mailbox
instead of in mbox.
Does not override the delete command.
\*(UA deviates from the POSIX standard with this command,
as a `next' command issued after `hold'
will display the following message,
not the current one.
.TP
.B if
Commands in \*(UA's startup files
can be executed conditionally
depending on whether the user is sending
or receiving mail with the if command.
For example:
.nf

    \fBif \fIreceive\fR
        \fIcommands .\ .\ .\fR
    \fBendif\fR

.fi
An else form is also available:
.nf

    \fBif \fIreceive\fR
        \fIcommands .\ .\ .\fR
    \fBelse\fR
        \fIcommands .\ .\ .\fR
    \fBendif\fR

.fi
Note that the only allowed conditions are
.BR receive ,
.BR send ,
and
.B term
(execute command if standard input is a tty).
.TP
.B ignore
Add the list of header fields named to the ignored list.
Header fields in the ignore list are not printed
on the terminal when a message is printed.
This command is very handy for suppression
of certain machine-generated header fields.
The Type and Print commands can be used
to print a message in its entirety,
including ignored fields.
If ignore is executed with no arguments,
it lists the current set of ignored fields.
.TP
.B imap
Sends command strings directly to the current IMAP server.
\*(UA operates always in IMAP \fIselected state\fR
on the current mailbox;
commands that change this
will produce undesirable results
and should be avoided.
Useful IMAP commands are:
.RS
.TP
.B create
Takes the name of an IMAP mailbox as an argument
and creates it.
.TP
.B 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.
.TP
.B 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 namespace prefix and a hierarchy separator is listed.
Not all IMAP servers support this command.
.RE
.TP
.B inc
Same as
.IR newmail .
.TP
.B junk
(j) Takes a list of messages
and marks all of them as junk mail.
Data from these messages is then inserted
into the junk mail database for future classification.
.TP
.B kill
(k) Takes a list of messages and `kills' them.
Killed messages are not printed in header summaries,
and are ignored by the
.I next
command.
The
.I kill
command also sets the score of the messages to negative infinity,
so that subsequent
.I score
commands will not unkill them again.
Killing is only effective for the current session on a folder;
when it is quit, all messages are automatically unkilled.
.TP
.B list
Prints the names of all available commands.
.TP
.B Mail
(M) Similar to
.IR mail ,
but saves the message in a file
named after the local part of the first recipient's address.
.TP
.B mail
(m) Takes as arguments the usual recipient addresses,
or asks on standard input if none were given;
then collects remain mail content and sends it out.
.TP
.B mbox
Indicate that a list of messages be sent
to mbox in the user's home directory when
\*(UA is quit.
This is the default action for messages
if unless the
.I hold
option is set.
\*(UA deviates from the POSIX standard with this command,
as a `next' command issued after `mbox'
will display the following message,
not the current one.
.TP
.B move
(mv) Acts like
.IR copy ,
but marks the messages for deletion
if they were transferred successfully.
.TP
.B Move
(Mv) Similar to
.IR move ,
but moves the messages to a file named after the local part
of the sender address of the first message.
.TP
.B 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
.I header
variable is set,
the headers of each new message are also printed.
.TP
.B next
(n) like + or CR) Goes to the next message
in sequence and types it.
With an argument list, types the next matching message.
.TP
.B New
Same as
.IR unread .
.TP
.B new
Same as
.IR unread .
.TP
.B online
Same as
.IR connect .
.TP
.B noop
If the current folder is located on an IMAP or POP3 server,
a NOOP command is sent.
Otherwise, no operation is performed.
.TP
.B Pipe
(Pi) Like
.I pipe
but also
pipes ignored header fields
and all parts of MIME
.I multipart/alternative
messages.
.TP
.B 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 \fIcmd\fR variable.
If the \fI page\fR variable is set,
every message is followed by a formfeed character.
.TP
.B preserve
(pre) A synonym for
.IR hold .
.TP
.B Print
(P) Like
.I print
but also
prints out ignored header fields
and all parts of MIME
.I multipart/alternative
messages.
See also
.IR print ,
.IR ignore ,
and
.IR retain .
.TP
.B print
(p) Takes a message list and types out each message
on the user's terminal.
If the message is a MIME multipart message,
all parts with a content type of `text' or `message' are shown,
the other are hidden except for their headers.
Messages are decrypted and converted to the terminal character set
if necessary.
.TP
.B probability
(prob) For each word given as argument,
the contents of its junk mail database entry are printed.
.TP
.B quit
(q) Terminates the session, saving all undeleted,
unsaved messages in the user's mbox file in his login directory,
preserving all messages marked with hold or preserve
or never referenced in his system mailbox,
and removing all other messages from his system mailbox.
If new mail has arrived during the session,
the message `\fIYou have new mail\fR' is given.
If given while editing a mailbox file with the \-f flag,
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.
.TP
.B redirect
(red) Same as
.IR resend .
.TP
.B Redirect
(Red) Same as
.IR Resend .
.TP
.B remove
(rem) Removes the named folders.
The user is asked for confirmation
in interactive mode.
.TP
.B rename
(ren) 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.
.TP
.B Reply
(R) Reply to originator.
Does not reply to other recipients
of the original message.
.TP
.BR reply
(r) Takes a message list and sends mail
to the sender and all recipients of the specified message.
The default message must not be deleted.
.TP
.B replyall
Similar to
.IR reply ,
but responds to all recipients regardless of the
.I flipr
and
.I Replyall
variables.
.TP
.B replysender
Similar to
.IR Reply ,
but responds to the sender only regardless of the
.I flipr
and
.I Replyall
variables.
.TP
.B Resend
Like
.IR 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.
.TP
.B resend
Takes a list of messages and a user name
and sends each message to the named user.
`Resent-From:' and related header fields are prepended
to the new copy of the message.
.TP
.B Respond
Same as
.IR Reply .
.TP
.B respond
Same as
.IR reply .
.TP
.B respondall
Same as
.IR replyall .
.TP
.B respondsender
Same as
.IR replysender .
.TP
.B retain
Add the list of header fields named to the retained list.
Only the header fields in the retain list are shown
on the terminal when a message is printed.
All other header fields are suppressed.
The Type and Print commands can be used
to print a message in its entirety.
If retain is executed with no arguments,
it lists the current set of retained fields.
.TP
.B Save
(S)
Similar to
.IR save ,
but saves the messages
in a file named after the local part
of the sender of the first message
instead of taking a filename argument.
.TP
.B 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 mbox file is used.
The filename in quotes,
followed by the line count and 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
.I \-f
command line option above.
.TP
.B savediscard
Same as saveignore.
.TP
.B saveignore
Saveignore is to save what ignore is to print and type.
Header fields thus marked are filtered out
when saving a message by save
or when automatically saving to 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.
.TP
.B saveretain
Saveretain is to save what retain is to print and type.
Header fields thus marked are the only ones
saved with a message when saving by save
or when automatically saving to mbox.
Saveretain overrides saveignore.
The use of this command is strongly discouraged
since it may strip header fields
that are needed to decode the message correctly.
.TP
.B score
(sc) Takes a message list and a floating point number
and adds the number to the score of each given message.
All messages start at score 0 when a folder is opened.
When the score of a message becomes negative, it is `killed'
with the effects described for the
.I kill
command;
otherwise if it was negative before and becomes positive,
it is `unkilled'.
Scores only refer to the currently opened instance of a folder.
.TP
.B set
(se) With no arguments, prints all variable values,
piped through the pager if the output does not fit on the screen.
Otherwise, sets option.
Arguments are of the form option=value
(no space before or after =)
or option.
Quotation marks may be placed around any part of the
assignment statement to quote blanks
or tabs, i.\|e. `\fIset indentprefix="\->"\fR'.
If an argument begins with
.BR no ,
as in `\fBset no\fIsave\fR',
the effect is the same as invoking the
.I unset
command with the remaining part of the variable
(`\fIunset \fIsave\fR').
.TP
.B seen
Takes a message list and marks all messages as having been read.
.TP
.B shell
(sh) Invokes an interactive version of the shell.
.TP
.B shortcut
Defines a shortcut name and its string for expansion,
as described for the
.I folder
command.
With no arguments,
a list of defined shortcuts is printed.
.TP
.B show
(Sh) Like
.IR print ,
but performs neither MIME decoding nor decryption
so that the raw message text is shown.
.TP
.B size
Takes a message list and prints out
the size in characters of each message.
.TP
.B sort
Create a sorted representation of the current folder,
and change the
.I 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
.I header
variable is set,
a header summary in the new order is also printed.
Possible sorting criteria are:
.RS
.TP
.B date
Sort the messages by their `Date:' field,
that is by the time they were sent.
.TP
.B from
Sort messages by the value of their `From:' field,
that is by the address of the sender.
If the
.I showname
variable is set,
the sender's real name (if any) is used.
.TP
.B size
Sort the messages by their size.
.TP
.B score
Sort the messages by their score.
.TP
.B status
Sort the messages by their message status
(new, read, old, etc.).
.TP
.B subject
Sort the messages by their subject.
.TP
.B thread
Create a threaded order,
as with the
.I thread
command.
.TP
.B to
Sort messages by the value of their `To:' field,
that is by the address of the recipient.
If the
.I showname
variable is set,
the recipient's real name (if any) is used.
.RE
.IP
If no argument is given,
the current sorting criterion is printed.
.TP
.B source
The source command reads commands from a file.
.TP
.B thread
(th) 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
.I 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
.I header
variable is set,
a header summary in threaded order is also printed.
.TP
.B top
Takes a message list and prints the top few lines of each.
The number of lines printed is controlled
by the variable toplines
and defaults to five.
.TP
.B touch
Takes a message list
and marks the messages for saving in the
.I mbox
file.
\*(UA deviates from the POSIX standard with this command,
as a `next' command issued after `mbox'
will display the following message,
not the current one.
.TP
.B Type
(T) Identical to the Print command.
.TP
.B type
(t) A synonym for print.
.TP
.B unalias
Takes a list of names defined by alias commands
and discards the remembered groups of users.
The group names no longer have any significance.
.TP
.B unanswered
Takes a message list and marks each message
as not having been answered.
.TP
.B uncollapse
(unc)
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.
.TP
.B undef
Undefines each of the named macros.
It is not an error to use a name that does not belong to
one of the currently defined macros.
.TP
.B undelete
(u) Takes a message list and marks each message as not being deleted.
.TP
.B undraft
Takes a message list and marks each message
as a draft.
.TP
.B unflag
Takes a message list and marks each message as not being `flagged'.
.TP
.B unfwdignore
Removes the header field names
from the list of ignored fields for the
.I forward
command.
.TP
.B unfwdretain
Removes the header field names
from the list of retained fields for the
.I forward
command.
.TP
.B ungood
Takes a message list and undoes the effect of a
.I good
command that was previously applied on exactly these messages.
.TP
.B unignore
Removes the header field names
from the list of ignored fields.
.TP
.B unjunk
Takes a message list and undoes the effect of a
.I junk
command that was previously applied on exactly these messages.
.TP
.B unkill
Takes a message list and `unkills' each message.
Also sets the score of the messages to 0.
.TP
.B Unread
Same as
.IR unread .
.TP
.B unread
(U) Takes a message list and marks each message
as not having been read.
.TP
.B unretain
Removes the header field names
from the list of retained fields.
.TP
.B unsaveignore
Removes the header field names
from the list of ignored fields for saving.
.TP
.B unsaveretain
Removes the header field names
from the list of retained fields for saving.
.TP
.B unset
Takes a list of option names and discards their remembered
values;
the inverse of set.
.TP
.B unshortcut
Deletes the shortcut names given as arguments.
.TP
.B unsort
Disable sorted or threaded mode (see the
.I sort
and
.I thread
commands), return to normal message order
and,
if the
.I header
variable is set,
print a header summary.
.TP
.B unthread
(unth) Same as
.IR unsort .
.TP
.B verify
(verif)
Takes a message list and verifies each message.
If a message is not an 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.
.TP
.B visual
(v) Takes a message list and invokes the display editor
on each message.
Modified contents are discarded
unless the
.I writebackedited
variable is set.
.TP
.B write
(w) For conventional messages the body without all headers is written.
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,
and the user is asked for a filename to save each other part.
For convience saving of each part may be skipped by giving an empty value;
the same result can also be achieved by writing it to '/dev/null'.
For the second and subsequent parts a leading '|' character causes the
part to be piped to the remainder of the user input interpreted as
a shell command;
otherwise the user input is expanded as usually for folders,
e.g., tilde expansion is performed.
In non-interactive mode, only the parts of the multipart message
that have a filename given in the part header are written,
the others are discarded.
The original message is never marked for deletion in the originating
mail folder.
For attachments,
the contents of the destination file are overwritten if the file
previously existed.
No special handling of compressed files is performed.
.TP
.B xit
(x) A synonym for exit.
.TP
.B z
\*(UA presents message headers in windowfuls
as described under the headers command.
The z command scrolls to the next window of messages.
If an argument is given,
it specifies the window to use.
A number prefixed by `+' or `\-' indicates
that the window is calculated in relation
to the current position.
A number without a prefix specifies an
absolute window number,
and a `$' lets \*(UA scroll
to the last window of messages.
.TP
.B Z
Similar to
.IR z ,
but scrolls to the next or previous window
that contains at least one new or `flagged' message.
.SS "Tilde escapes"
Here is a summary of the tilde escapes,
which are used when composing
messages to perform special functions.
Tilde escapes are only recognized
at the beginning of lines.
The name `\fItilde escape\fR' is somewhat of a misnomer
since the actual escape character can be set
by the option escape.
.TP
.BI ~! command
Execute the indicated shell command,
then return to the message.
.TP
.B ~.
Same effect as typing the end-of-file character.
.TP
.BI ~< filename
Identical to ~r.
.TP
.BI ~<! command
Command is executed using the shell.
Its standard output is inserted into the message.
.TP
\fB~@\fR [\fIfilename\fR .\ .\ . ]
With no arguments, edit the attachment list.
First, the user can edit all existing attachment data.
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 file name is given.
If \fIfilename\fP arguments are specified,
all of them are appended to the end of the attachment list.
Filenames which contain white space
can only be specified
with the first method (no \fIfilename\fP arguments).
.TP
.B ~A
Inserts the string contained in the
.I Sign
variable
(same as `~i Sign').
The escape sequences `\fB\et\fR' (tabulator) and `\fB\en\fR' (newline)
are understood.
.TP
.B ~a
Inserts the string contained in the
.B sign
variable
(same as `~i sign').
The escape sequences `\fB\et\fR' (tabulator) and `\fB\en\fR' (newline)
are understood.
.TP
.BI ~b "name .\ .\ ."
Add the given names to the list of carbon copy recipients
but do not make the names visible in the Cc: line
(`blind' carbon copy).
.TP
.BI ~c "name .\ .\ ."
Add the given names to the list of carbon copy recipients.
.TP
.B ~d
Read the file `dead.letter' from the user's home directory
into the message.
.TP
.B ~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.
.TP
.BI ~f messages
Read the named messages into the message being sent.
If no messages are specified,
read in the current message.
Message headers currently being ignored
(by the ignore or retain command)
are not included.
For MIME multipart messages,
only the first printable part is included.
.TP
.BI ~F messages
Identical to ~f, except all message headers and
all MIME parts are included.
.TP
.B ~h
Edit the message header fields
`To:', `Cc:', `Bcc:', and `Subject:'
by typing each one in turn
and allowing the user to append text
to the end or modify the field
by using the current terminal erase and kill characters.
.TP
.B ~H
Edit the message header fields
`From:', `Reply-To:', `Sender:', and `Organization:'
in the same manner as described for
.IR ~h .
The default values for these fields originate from the
.IR from ,
.IR replyto ,
and
.I ORGANIZATION
variables.
If this tilde command has been used,
changing the variables has no effect on the current message anymore.
.TP
.BI ~i variable
Insert the value of the specified variable
into the message adding a newline character at the end.
If the variable is unset or empty,
the message remains unaltered.
The escape sequences `\fB\et\fR' (tabulator) and `\fB\en\fR' (newline)
are understood.
.TP
.BI ~m messages
Read the named messages into the message being sent,
indented by a tab or by the value of indentprefix.
If no messages are specified,
read the current message.
Message headers currently being ignored
(by the ignore or retain command)
are not included.
For MIME multipart messages,
only the first printable part is included.
.TP
.BI ~M messages
Identical to ~m, except all message headers and
all MIME parts are included.
.TP
.B ~p
Print out the message collected so far,
prefaced by the message header fields
and followed by the attachment list, if any.
If the message text is longer than the screen size,
it is piped through the pager.
.TP
.B ~q
Abort the message being sent,
copying the message to
`dead.letter' in the user's home directory
if save is set.
.TP
.BI ~r filename
Read the named file into the message.
.TP
.BI ~s string
Cause the named string to become the current subject field.
.TP
.BI ~t "name .\ .\ ."
Add the given names to the direct recipient list.
.TP
.B ~v
Invoke an alternate editor
(defined by the 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.
.TP
.BI ~w filename
Write the message onto the named file.
If the file exists,
the message is appended to it.
.TP
.B ~x
Same as ~q,
except that the message is not saved to the `dead.letter' file.
.TP
.BI ~| command
Pipe the message through the command as a filter.
If the command gives no output or terminates abnormally,
retain the original text of the message.
The command
.IR fmt (1)
is often used
as command to rejustify the message.
.TP
.BI ~: \*(ua-command
Execute the given \*(UA command.
Not all commands, however, are allowed.
.TP
.BI ~_ \*(ua-command
Identical to ~:.
.TP
.BI ~~ string
Insert the string of text in the message
prefaced by a single ~.
If the escape character has been changed,
that character must be doubled
in order to send it at the beginning of a line.
.SS "Variable options"
Options are controlled via set and unset commands,
see their entries for a syntax description.
An option is also set
if it is passed to \*(UA
as part of the environment
(this is not restricted to specific variables as in the POSIX standard).
A value given in a startup file overrides
a value imported from the environment.
Options may be either binary,
in which case it is only significant
to see whether they are set or not;
or string, in which case the actual value is of interest.
.SS "Binary options"
.PP
The binary options include the following:
.TP
.B 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.
.TP
.B allnet
Causes only the local part to be evaluated
when comparing addresses.
.TP
.B append
Causes messages saved in mbox to be appended to the end
rather than prepended.
This should always be set.
.TP
.BR ask \ or \ 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.
.TP
.B askatend
Causes the prompts for `Cc:' and `Bcc:' lists
to appear after the message has been edited.
.TP
.B askattach
If set, \*(UA asks for files to attach at the end of each message.
Responding with a newline indicates not to include an attachment.
.TP
.B askcc
Causes the user to be prompted
for additional carbon copy recipients
(at the end of each message if
.I askatend
or
.I bsdcompat
is set).
Responding with a newline
indicates the user's satisfaction with the current list.
.TP
.B askbcc
Causes the user to be prompted
for additional blind carbon copy recipients
(at the end of each message if
.I askatend
or
.I bsdcompat
is set).
Responding with a newline
indicates the user's satisfaction with the current list.
.TP
.B asksign
Causes the user to be prompted
if the message is to be signed
at the end of each message.
The
.I smime-sign
variable is ignored when this variable is set.
.TP
.B autocollapse
Causes threads to be collapsed automatically when
threaded mode is entered
(see the
.I collapse
command).
.TP
.B autoinc
Same as
.IR newmail .
.TP
.B autoprint
Causes the delete command to behave like dp \-
thus, after deleting a message,
the next one will be typed automatically.
.TP
.B autothread
Causes threaded mode (see the
.I thread
command) to be entered automatically
when a folder is opened.
.TP
.B bang
Enables the substitution of `\fB!\fR'
by the contents of the last command line
in shell escapes.
.TP
.B bsdannounce
Causes automatic display of a header summary after executing a
.I folder
command.
.TP
.B bsdcompat
Sets some cosmetical features to traditional BSD style;
has the same affect as setting `askatend' and
all other variables prefixed with `bsd',
setting prompt to `&\ ', and changing the default pager to
.IR more .
.TP
.B bsdflags
Changes the letters printed in the first column of a header summary
to traditional BSD style.
.TP
.B bsdheadline
Changes the display of columns in a header summary
to traditional BSD style.
.TP
.B bsdmsgs
Changes some informational messages
to traditional BSD style.
.TP
.B bsdorder
Causes the `Subject:' field to appear
immediately after the `To:' field
in message headers and with the
.I ~h
tilde command.
.TP
.B bsdset
Changes the output format of the
.I set
command to traditional BSD style.
.TP
.B chained-junk-tokens
Normally, the Bayesian junk mail filter bases its classifications
on single word tokens extracted from messages.
If this option is set,
adjacent words are combined to pairs,
which are then used as additional tokens.
This usually improves the accuracy of the filter,
but also increases the junk mail database
five- to tenfold.
.TP
.B datefield
The date in a header summary
is normally the date of the mailbox `From\ ' line of the message.
If this variable is set,
the date as given in the `Date:' header field is used,
converted to local time.
.TP
.B debug
Prints debugging messages and disables the actual delivery of messages.
Unlike
.IR verbose ,
this option is intended for \*(UA development only.
.TP
.B disconnected
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
.IR imap-cache ).
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 `copy * /dev/null' can be used
while still in
.I online
mode.
Changes that are made to IMAP mailboxes in disconnected mode
are queued and committed later
when a connection to that server is opened in online mode.
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 `dead.letter' when this problem occurs.
.TP
\fBdisconnected-\fIuser\fB@\fIhost\fR
The specified account is handled as described for the
.I disconnected
variable above,
but other accounts are not affected.
.TP
.B dot
The binary option dot causes \*(UA to interpret
a period alone on a line
as the terminator of a message the user is sending.
.TP
.B editheaders
When a message is edited while being composed,
its header is included in the editable text.
`To:', `Cc:', `Bcc:', `Subject:', `From:', `Reply-To:', `Sender:',
and 'Organization:'
fields are accepted within the header,
other fields are ignored.
.TP
.B emptybox
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.
.TP
.B emptystart
If the mailbox is empty,
\*(UA normally prints \fI`No mail for user'\fR
and exits immediately.
If this option is set,
\*(UA starts even with an empty mailbox.
.TP
.B flipr
Exchanges the
.I Respond
with the
.I respond
commands and vice-versa.
.TP
.B forward-as-attachment
Original messages are normally sent as inline text with the
.I forward
command,
and only the first part of a multipart message is included.
With this option,
messages are sent as MIME
.I message/rfc822
attachments,
and all of their parts are included.
The
.I fwdignore
and
.I fwdretain
options are ignored when the
.I forward-as-attachment
option is set.
.TP
.B fullnames
When replying to a message,
\*(UA normally removes the comment parts of email addresses,
which by convention contain the full names of the recipients.
If this variable is set,
such stripping is not performed,
and comments are retained.
.TP
.B 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.
.TP
.B hold
This option is used to hold messages
in the system mailbox by default.
.TP
.B idna-disable
Unless this is set domain names that fail to pass their content test are
handed over to the IDNA (internationalized domain names for applications)
converter, and, in case the encoding succeeds,
are replaced with the converted version.
Because the domain names are expected to be in locale encoding,
a locale which uses the UTF-8 charset is required to represent all
possible international domain names.
(Note that the \fIttycharset\fR option does not affect IDNA encoding.)
.TP
.B idna-strict-checks
If this is set (and \fIidna-disable\fR is not),
then the IDNA-conversion is enforced to apply stricter error checking in
respect to the content of domain names.
Also, a successfully encoded (and thus normalized) domain name is
converted back to the locale version, so that special TLD (top-level
domain) checks can be performed on it;
e.g., the \fI.no\fR TLD does not allow the Euro currency symbol,
but only this strict check will catch this error.
.TP
.B ignore
Causes interrupt signals from the terminal
to be ignored and echoed as @'s.
.TP
.B ignoreeof
An option related to dot is ignoreeof
which makes \*(UA refuse to
accept a control-d as the end of a message.
Ignoreeof also applies to \*(UA command mode.
.TP
.B imap-use-starttls
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.
.TP
\fBimap-use-starttls-\fIuser\fB@\fIhost\fR
Activates
.I imap-use-starttls
for a specific account.
.TP
.B keep
This option causes \*(UA to truncate the user's system mailbox
instead of deleting it when it is empty.
This should always be set,
since it prevents malicious users
from creating fake mail folders
in a world-writable spool directory.
.TP
.B 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.
.TP
.B 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.
.TP
.B metoo
Usually, when a group is expanded
that contains the sender,
the sender is removed from the expansion.
Setting this option causes
the sender to be included in the group.
.TP
.B 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
.I maildir
folder must be re-scanned to determine
if new mail has arrived.
.IP
If this variable is set to the special value
.BR 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.
A
.I maildir
folder is not scanned then.
.IP
In any case,
the IMAP server may send notifications about messages
that have been deleted on the server
by another process or client.
In this case, `Expunged \fIn\fR messages' is printed
regardless of this variable,
and message numbers may have changed.
.TP
.B noheader
Setting the option noheader is the same
as giving the \-N flag on the command line.
.TP
.B outfolder
Causes the filename given in the
.I record
variable
and the sender-based filenames for the
.I Copy
and
.I Save
commands
to be interpreted relative to the directory given in the
.I folder
variable rather than to the current directory
unless it is an absolute pathname.
.TP
.B page
If set, each message the \fIpipe\fR command prints out
is followed by a formfeed character.
.TP
.B piperaw
Send messages to the
.I pipe
command without performing MIME and character set conversions.
.TP
.B pop3-use-apop
If this variable is set,
the APOP authentication method is used
when a connection to a POP3 server is initiated.
The advantage of this method over the usual USER/PASS authentication is
that the password is not sent over the network in clear text.
The connection fails
if the server does not support the APOP command.
.TP
\fBpop3-use-apop-\fIuser\fB@\fIhost\fR
Enables
.I pop3-use-apop
for a specific account.
.TP
.B pop3-use-starttls
Causes \*(UA to issue a 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.
.TP
\fBpop3-use-starttls-\fIuser\fB@\fIhost\fR
Activates
.I pop3-use-starttls
for a specific account.
.TP
.B 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.
.TP
.B print-alternatives
When a MIME message part of type
.I multipart/alternative
is displayed and it contains a subpart of type
.IR 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
.IR multipart/mixed .
.TP
.B quiet
Suppresses the printing of the version when first invoked.
.TP
.B recipients-in-cc
On group replies, specify only the sender of the original mail
in \fI`To:'\fR and mention it's other recipients in the secondary
\fI`Cc:'\fR.
.TP
.B record-resent
If both this variable and the
.I record
variable are set,
the
.I resend
and
.I Resend
commands save messages to the
.I record
folder as it is normally only done for newly composed messages.
.TP
.B 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
.I sendcharsets
variable is evaluated as usual.
.TP
.B Replyall
Reverses the sense of reply and Reply commands.
.TP
.B rfc822-no-body-from_
By default \*(UA shows a so-called "From " line when a message contains
another message via the message/rfc822 MIME mechanism.
This may be misleading since it intransparently adds content on the
one hand,
and also silently maps any missing information from the envelope mail
onto the embedded one on the other.
If this value is set then no "From " line is shown for embedded
message/rfc822 mail messages.
.TP
.B rfc822-show-all
Messages or MIME message parts that embed entire mail message via the
message/rfc822 MIME mechanism do not print/show/quote headers of the
embedded message but after filtering them through the normal mechanism.
If this value is set then an embedded mail is treated as a unity.
.TP
.B save
When the user aborts a message
with two RUBOUT (interrupt characters)
\*(UA copies the partial letter
to the file `dead.letter' in the home directory.
This option is set by default.
.TP
.B searchheaders
If this option is set, then
a message-list specifier in the form `\fI/x:y\fR'
will expand to all messages containing
the substring `\fIy\fR' in the header field `\fIx\fR'.
The string search is case insensitive.
.TP
.B sendwait
When sending a message,
wait until the mail transfer agent exits
before accepting further commands.
If the mail transfer agent returns a non-zero exit status,
the exit status of \*(ua will also be non-zero.
.TP
.B showlast
Setting this option causes \*(UA to start at the
last message instead of the first one when opening a mail folder.
.TP
.B showname
Causes \*(UA
to use the sender's real name instead of the plain address
in the header field summary and in message specifications.
.TP
.B showto
Causes the recipient of the message to be shown in the header summary
if the message was sent by the user.
.TP
.B 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
.I \-E
option).
.TP
.B smime-force-encryption
Causes \*(UA
to refuse sending unencrypted messages.
.TP
.B smime-sign
If this variable is set,
outgoing messages are S/MIME signed with the user's private key.
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.
.TP
.B smime-no-default-ca
Do not load the default CA locations
when verifying S/MIME signed messages.
Only applicable if S/MIME support is built using OpenSSL.
.TP
.B smtp-use-starttls
Causes \*(UA to issue a STARTTLS command
to make an SMTP session SSL/TLS encrypted.
Not all servers support this command;
because of common implementation defects,
it cannot be automatically determined
whether a server supports it or not.
.TP
.B ssl-no-default-ca
Do not load the default CA locations
to verify SSL/TLS server certificates.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-v2-allow
Accept SSLv2 connections.
These are normally not allowed
because this protocol version is insecure.
.TP
.B verbose
Setting the option verbose is the same
as using the \-v flag on the command line.
When \*(UA runs in verbose mode,
details of the actual message delivery
and protocol conversations for IMAP, POP3, and SMTP,
as well as of other internal processes,
are displayed on the user's terminal,
This is sometimes useful to debug problems.
\*(UA prints all data that is sent to remote servers in clear texts,
including passwords,
so care should be taken that no unauthorized option
can view the screen if this option is enabled.
.TP
.B writebackedited
If this variable is set,
messages modified using the
.I edit
or
.I visual
commands are written back to the current folder when it is quit.
This is only possible for writable folders in
.I mbox
format.
Setting this variable also disables
MIME decoding and decryption for the editing commands.
.SS "String Options"
.PP
The string options include the following:
.TP
.B attrlist
A sequence of characters to print in the `attribute'
column of a header summary,
each for one type of messages in the following order:
new,
unread but old,
new but read,
read and old,
saved,
preserved,
mboxed,
flagged,
answered,
draft,
killed,
start of a collapsed thread,
collapsed,
classified as junk.
The default is `NUROSPMFATK+\-J',
or `NU\ \ *HMFATK+\-J' if
.I bsdflags
or the
.I SYSV3
environment variable
are set.
.TP
.B autobcc
Specifies a list of recipients to which
a blind carbon copy of each outgoing message
will be sent automatically.
.TP
.B autocc
Specifies a list of recipients to which
a carbon copy of each outgoing message
will be sent automatically.
.TP
.B autosort
Causes sorted mode (see the
.I sort
command) to be entered automatically
with the value of this option as sorting method
when a folder is opened.
.TP
.B cmd
The default value for the \fIpipe\fR command.
.TP
.B crt
The valued option crt is used as a threshold
to determine how long a message must be
before PAGER is used to read it.
If crt is set without a value,
then the height of the terminal screen stored in the system
is used to compute the threshold (see
.IR stty (1)).
.TP
.B DEAD
The name of the file to use
for saving aborted messages.
This defaults to `dead.letter'
in the user's home directory.
.TP
.B EDITOR
Pathname of the text editor to use
in the edit command and ~e escape.
If not defined,
then a default editor is used.
.TP
.B encoding
The default MIME encoding to use
in outgoing text messages and message parts.
Valid values are \fI8bit\fR or \fIquoted-printable\fR.
The default is \fI8bit\fR.
In case the mail transfer system
is not ESMTP compliant,
\fIquoted-printable\fR should be used instead.
If there is no need to encode a message,
\fI7bit\fR transfer mode is used,
without regard to the value of this variable.
Binary data is always encoded in \fIbase64\fR mode.
.TP
.B escape
If defined, the first character of this option
gives the character to use in the place of ~ to denote escapes.
.TP
.B folder
The name of the directory to use
for storing folders of messages.
All folder names that begin with `+'
refer to files below that directory.
If the directory name begins with a `/',
\*(UA considers it to be an absolute pathname;
otherwise, the folder directory is found
relative to the user's home directory.
.IP
The directory name may also refer to an IMAP account;
any names that begin with `+'
then refer to IMAP mailboxes on that account.
An IMAP folder is normally given in the form
.sp
.nf
    imaps://mylogin@imap.myisp.example
.fi
.sp
In this case,
the `+' and `@' prefixes for folder names
have the same effect
(see the
.I folder
command).
.IP
Some IMAP servers do not accept the creation of mailboxes
in the hierarchy base;
they require that they are created as subfolders of `INBOX'.
With such servers,
a folder name of the form
.sp
.nf
    imaps://mylogin@imap.myisp.example/INBOX.\&
.fi
.sp
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
.I imap namespace
command for a method to detect the appropriate prefix and delimiter.
.TP
.B 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.
.TP
\fBfolder-hook-\fIfullname\fR
When a folder named
.I fullname
is opened,
the macro corresponding to the value of this variable is executed.
Unlike other folder specifications,
the fully expanded name of a folder, without metacharacters,
is used to avoid ambiguities.
The macro specified with
.I folder-hook
is not executed if this variable is effective for a folder
(unless it is explicitly invoked within the called macro).
.TP
.B from
The address (or a list of addresses)
to put into the \fI`From:'\fR field of the message header.
If replying to a message,
these addresses are handled as if they were in the alternates list.
.\" If this variable is set,
.\" a \fI`Sender:'\fR field containing the user's name
.\" is also generated,
.\" unless the variable \fIsmtp\fR is set
.\" and its value differs from \fIlocalhost\fR.
If the machine's hostname is not valid at the Internet
(for example at a dialup machine),
either this variable or
.I hostname
have to be set or \*(UA will not generate Message-ID header fields
but leave that task up to a (obviously present) local Mail Transfer
Agent (MTA).
If
.I from
contains more than one address,
the
.I sender
variable must also be set.
.TP
.B fwdheading
The string to print before the text of a message
with the
.I forward
command
(unless the
.I forward-as-attachment
variable is set).
Defaults to ``-------- Original Message --------'' if unset.
If it is set to the empty string,
no heading is printed.
.TP
.B headline
A format string to use for the header summary,
similar to
.I printf
formats.
A `%' character introduces a format specifier.
It may be followed by a number indicating the field width.
If the field is a number,
the width may be negative,
which indicates that it is to be left-aligned.
Valid format specifiers are:
.sp
.in +4m
.TS
l4fB l.
%a      Message attributes.
%c      The score of the message.
%d      The date when the message was received.
%e      The indenting level in threaded mode.
%f      The address of the message sender.
%i      The message thread structure.
%l      The number of lines of the message.
%m      Message number.
%o      The number of octets (bytes) in the message.
%s      Message subject (if any).
%S      Message subject (if any) in double quotes.
%t      The position in threaded/sorted order.
%>      A `>' for the current message, otherwise ` '.
%<      A `<' for the current message, otherwise ` '.
%%      A `%' character.
.TE
.in -4m
.IP
The default is `%>\&%a\&%m\ %18f\ %16d\ %4l/%\-5o\ %i%s',
or `%>\&%a\&%m\ %20f\ \ %16d\ %3l/%\-5o\ %i%S' if
.I bsdcompat
is set.
.TP
.B hostname
Use this string as hostname
when expanding local addresses instead of the value obtained from
.IR uname (2)
and
.IR getaddrinfo (3).
Note that this must be set explicitly to become used for the
generation of Message-ID fields.
.TP
.B imap-auth
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 GSSAPI-based authentication.
.TP
\fBimap-auth-\fIuser\fB@\fIhost\fR
Sets the IMAP authentication method for a specific account.
.TP
.B imap-cache
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.
.TP
.B imap-keepalive
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
.I value
greater than 0
causes a NOOP command to be sent each
.I value
seconds if no other operation is performed.
.TP
.B imap-list-depth
When retrieving the list of folders on an IMAP server, the
.I 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
.I folders
command does not descend to subfolders.
.TP
.B indentprefix
String used by the `\fI~m\fR' and `\fI~M\fR' tilde escapes
and by the \fIquote\fR option
for indenting messages,
in place of the normal tab character (^I).
Be sure to quote the value
if it contains spaces or tabs.
.TP
.B junkdb
The location of the junk mail database.
The string is treated like a folder name,
as described for the
.I folder
command.
.IP
The files in the junk mail database are normally stored in
.IR compress (1)
format for saving space.
If processing time is considered more important,
.IR uncompress (1)
can be used to store them in plain form.
\*(UA will then work using the uncompressed files.
.TP
.B LISTER
Pathname of the directory lister
to use in the
.I folders
command
when operating on local mailboxes.
Default is /bin/ls.
.TP
.B MAIL
Is used as the user's mailbox, if set.
Otherwise, a system-dependent default is used.
Can be a
\fIprotocol\fB://\fR
string (see the
.I folder
command for more information).
.TP
.B MBOX
The name of the mbox file.
It can be the name of a folder.
The default is `\fImbox\fR' in the user's home directory.
.TP
.B NAIL_EXTRA_RC
The name of an optional startup file to be read after \*(ur.
This variable is ignored if it is imported from the environment;
it has an effect only if it is set in \*(UR or \*(ur to allow bypassing the
configuration with e. g. `MAILRC=/dev/null'.
Use this file for commands that are not understood by other \*(UA
implementations.
.TP
.B NAIL_HEAD
A string to put at the beginning of each new message.
The escape sequences `\fB\et\fR' (tabulator) and `\fB\en\fR' (newline)
are understood.
.TP
.B NAIL_TAIL
A string to put at the end of each new message.
The escape sequences `\fB\et\fR' (tabulator) and `\fB\en\fR' (newline)
are understood.
.TP
.B maximum-unencoded-line-length
Messages that contain lines longer than the value of this variable
are encoded in quoted-printable
even if they contain only ASCII characters.
The maximum effective value is 950.
If set to 0,
all ASCII text messages are encoded in quoted-printable.
S/MIME signed messages are always encoded
in quoted-printable regardless of the value of this variable.
.TP
.B newfolders
If this variable has the value
.BR maildir ,
newly created local folders will be in
.I maildir
format.
.TP
.B nss-config-dir
A directory that contains the files
.RI cert N .db
to retrieve certificates,
.RI key N .db
to retrieve private keys,
and secmod.db,
where
.I N
is a digit.
These are usually taken from Mozilla installations,
so an appropriate value might be
`~/.mozilla/firefox/default.clm'.
\*(UA opens these files read-only
and does not modify them.
However, if the files are modified by Mozilla
while \*(UA is running,
it will print a `Bad database' message.
It may be necessary to create copies of these files
that are exclusively used by \*(UA then.
Only applicable if S/MIME and SSL/TLS support is built using
Network Security Services (NSS).
.TP
.B ORGANIZATION
The value to put into the \fI`Organization:'\fR field of the message header.
.TP
.B PAGER
Pathname of the program to use
in the more command
or when crt variable is set.
The default paginator
.IR pg (1)
or, in BSD compatibility mode,
.IR more (1)
is used
if this option is not defined.
.TP
\fBpassword-\fIuser\fB@\fIhost\fR
Set the password for
.I user
when connecting to
.IR 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.
.TP
.BI pipe- content/subcontent
When a MIME message part of
.I content/subcontent
type is displayed or it is replied to,
its text is filtered through the value of this variable
interpreted as a shell command.
Special care must be taken when using such commands
as mail viruses may be distributed by this method;
if messages of type
.I application/x-sh
were filtered through the shell, for example,
a message sender could easily execute arbitrary code
on the system \*(UA is running on.
.TP
.B pop3-keepalive
POP3 servers may 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
.I value
greater than 0
causes a NOOP command to be sent each
.I value
seconds if no other operation is performed.
.TP
.B prompt
The string printed when a command is accepted.
Defaults to `\fB?\ \fR',
or to `\fB&\ \fR' if the
.I bsdcompat
variable is set.
.TP
.B quote
If set, \*(UA starts a replying message with the original message
prefixed by the value of the variable \fIindentprefix\fR.
Normally, a heading consisting of `Fromheaderfield wrote:' is printed
before the quotation.
If the string \fInoheading\fR is assigned to the \fIquote\fR variable,
this heading is omitted.
If the string \fIheaders\fR is assigned,
the headers selected by the ignore/retain commands
are printed above the message body,
thus \fIquote\fR acts like an automatic ~m command then.
If the string \fIallheaders\fR is assigned,
all headers are printed above the message body,
and all MIME parts are included,
thus \fIquote\fR acts like an automatic ~M command then.
.TP
.B quote-fold
If set in addition to \fIindentprefix\fR, \*(UA interprets this
number as the maximum line length of the quotation when replying to a
message.
Setting this turns on a more fancy quotation algorithm in that leading
quotation characters are compressed and overlong lines are folded to
\fIquote-fold\fR characters each, breaking at whitespace as necessary
and starting the follow lines with fillers to pad up to the last
quotation markers width.
The value of \fIquote-fold\fR can't be smaller than the length of
\fIindentprefix\fR plus some additional pad.  It is automatically
adjusted to the minimum as necessary.
.TP
.B record
If defined, gives the pathname of the folder
used to record all outgoing mail.
If not defined,
then outgoing mail is not so saved.
When saving to this folder fails,
the message is not sent
but saved to the `dead.letter' file instead.
.TP
.B replyto
A list of addresses to put into the \fI`Reply-To:'\fR field
of the message header.
If replying to a message, such addresses are handled
as if they were in the alternates list.
.TP
.B 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 z command.
.TP
.B sendcharsets
A comma-separated list of character set names
that can be used in Internet mail.
When a message that contains characters not representable in US-ASCII
is prepared for sending,
\*(UA tries to convert its text
to each of the given character sets in order
and uses the first appropriate one.
The default is `utf-8'.
.IP
Character sets assigned to this variable should be ordered
in ascending complexity.
That is, the list should start with e.\|g.
`iso-8859-1' for compatibility with older mail clients,
might contain some other language-specific character sets,
and should end with `utf-8'
to handle messages that combine texts in multiple languages.
.TP
.B sender
An address that is put into the `Sender:' field
of outgoing messages.
This field needs not normally be present.
It is, however, required
if the `From:' field contains more than one address.
It can also be used to indicate that a message
was sent on behalf of somebody other;
in this case, `From:' should contain the address
of the person that took responsibility for the message,
and `Sender:' should contain the address
of the person that actually sent the message.
The
.I sender
address is handled as if it were in the
.I alternates
list.
.TP
.B sendmail
To use an alternate mail delivery system,
set this option to the full pathname of the program to use.
.TP
.B SHELL
Pathname of the shell to use
in the ! command and the ~! escape.
A default shell is used
if this option is not defined.
.TP
.B Sign
A string for use with the
.I ~A
command.
.TP
.B sign
A string for use with the
.I ~a
command.
.TP
.B 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.
.TP
.B smime-ca-dir
Specifies a directory with CA certificates for verification
of S/MIME signed messages.
The format is the same as described in
.IR SSL_CTX_load_verify_locations (3).
Only applicable if S/MIME support is built using OpenSSL.
.TP
.B smime-ca-file
Specifies a file with CA certificates for verification
of S/MIME signed messages.
The format is the same as described in
.IR SSL_CTX_load_verify_locations (3).
Only applicable if S/MIME support is built using OpenSSL.
.TP
\fBsmime-cipher-\fIuser@host\fR
Specifies a cipher to use when generating S/MIME encrypted messages
for
.IR user@host .
Valid ciphers are
.B rc2-40
(RC2 with 40 bits),
.B rc2-64
(RC2 with 64 bits),
.B des
(DES, 56 bits)
and
.B des-ede3
(3DES, 112/168 bits).
The default is 3DES.
It is not recommended to use the other ciphers
unless a recipient's client is actually unable to handle 3DES
since they are comparatively weak;
but even so, the recipient should upgrade his software in preference.
.TP
.B smime-crl-file
Specifies a file that contains a CRL in PEM format
to use when verifying S/MIME messages.
Only applicable if S/MIME support is built using OpenSSL.
.TP
.B smime-crl-dir
Specifies a directory that contains files with CRLs in PEM format
to use when verifying S/MIME messages.
Only applicable if S/MIME support is built using OpenSSL.
.TP
\fBsmime-encrypt-\fIuser@host\fR
If this variable is set,
messages to
.I user@host
are encrypted before sending.
If S/MIME support is built using OpenSSL,
the value of the variable must be set to the name of a file
that contains a certificate in PEM format.
If S/MIME support is built using NSS,
the value of this variable is ignored,
but if multiple certificates for
.I user@host
are available, the
.I smime-nickname-user@host
variable should be set.
Otherwise a certificate for the recipient
is automatically retrieved from the certificate database,
if possible.
.IP
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
.I smime-force-encryption
variable is set.
It is recommended to sign encrypted messages,
i.\|e. to also set the
.I smime-sign
variable.
.TP
\fBsmime-nickname-\fIuser@host\fR
Specifies the nickname of a certificate
to be used when encrypting messages for
.I user@host .
Only applicable if S/MIME support is built using NSS.
.TP
.B smime-sign-cert
Points to a file in PEM format
that contains the user's private key
as well as his certificate.
Both are used with S/MIME
for signing and decrypting messages.
Only applicable if S/MIME support is built using OpenSSL.
.TP
\fBsmime-sign-cert-\fIuser@host\fR
Overrides
.I smime-sign-cert
for the specific addresses.
When signing messages and the value of the
.I from
variable is set
to
.IR user@host ,
the specific file is used.
When decrypting messages,
their recipient fields (To: and Cc:) 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.
Only applicable if S/MIME support is built using OpenSSL.
.TP
.B smime-sign-include-certs
If used, this must be set to 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
.IR smime-sign-cert
certificate.
This is most useful for long certificate chains if it is
desired to aid the receiving party's verification process.
Only applicable if S/MIME support is built using OpenSSL.
.TP
\fBsmime-sign-include-certs-\fIuser@host\fR
Overrides
.I smime-sign-include-certs
for the specific addresses.
Refer to the discussion of \fBsmime-sign-cert-\fIuser@host\fR
for more on this topic.
.TP
.B smime-sign-nickname
Specifies that the named certificate be used for signing mail.
If this variable is not set,
but a single certificate matching the current
.I from
address is found in the database,
that one is used automatically.
Only applicable if S/MIME support is built using NSS.
.TP
\fBsmime-sign-nickname-\fIuser@host\fR
Overrides
.I smime-sign-nickname
for a specific address.
Only applicable if S/MIME support is built using NSS.
.TP
.B smtp
Normally, \*(UA invokes \fIsendmail(1)\fR directly to transfer messages.
If the \fIsmtp\fR variable is set, a SMTP connection to the server
specified by the value of this variable is used instead.
If the SMTP server does not use the standard port,
a value of \fIserver:port\fR can be given,
with \fIport\fR as a name or as a number.
.IP
There are two possible methods to get SSL/TLS encrypted SMTP sessions:
First, the STARTTLS command can be used to encrypt a session
after it has been initiated,
but before any user-related data has been sent; see
.I \%smtp-use-starttls
above.
Second, some servers accept sessions that are encrypted
from their beginning on. This mode is configured by assigning
\fBsmtps://\fIserver\fR[\fB:\fIport\fR]
to the
.I smtp
variable.
.IP
The SMTP transfer is executed in a child process;
unless either the
.I sendwait
or the
.I verbose
variable is set,
this process runs asynchronously.
If it receives a TERM signal,
it will abort and save the message to the `dead.letter' file.
.TP
.B smtp-auth
Sets the SMTP authentication method.
If set to `login',
or if unset and smtp-auth-user is set,
AUTH LOGIN is used.
If set to `cram-md5',
AUTH CRAM-MD5 is used;
if set to `plain',
AUTH PLAIN is used.
Otherwise,
no SMTP authentication is performed.
.TP
\fBsmtp-auth-\fIuser\fB@\fIhost\fR
Overrides
.I smtp-auth
for specific values of sender addresses,
depending on the
.I from
variable.
.TP
.B smtp-auth-password
Sets the global password for SMTP AUTH.
Both user and password have to be given
for AUTH LOGIN and AUTH CRAM-MD5.
.TP
\fBsmtp-auth-password-\fIuser\fB@\fIhost\fR
Overrides
.I smtp-auth-password
for specific values of sender addresses,
depending on the
.I from
variable.
.TP
.B smtp-auth-user
Sets the global user name for SMTP AUTH.
Both user and password have to be given
for AUTH LOGIN and AUTH CRAM-MD5.
.IP
If this variable is set but neither
.I smtp-auth-password
or a matching
.I smtp-auth-password-user@host
can be found,
\*(UA will as for a password on the user's terminal.
.TP
\fBsmtp-auth-user-\fIuser\fB@\fIhost\fR
Overrides
.I smtp-auth-user
for specific values of sender addresses,
depending on the
.I from
variable.
.TP
.B ssl-ca-dir
Specifies a directory with CA certificates for verification
of SSL/TLS server certificates.
See
.IR SSL_CTX_load_verify_locations (3)
for more information.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-ca-file
Specifies a file with CA certificates for verification
of SSL/TLS server certificates.
See
.IR SSL_CTX_load_verify_locations (3)
for more information.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-cert
Sets the file name 
for a SSL/TLS client certificate
required by some servers.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
\fBssl-cert-\fIuser\fB@\fIhost\fR
Sets an account-specific file name
for a SSL/TLS client certificate
required by some servers.
Overrides
.I ssl-cert
for the specified account.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-cipher-list
Specifies a list of ciphers for SSL/TLS connections.
See ciphers(1) for more information.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-crl-file
Specifies a file that contains a CRL in PEM format
to use when verifying SSL/TLS server certificates.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-crl-dir
Specifies a directory that contains files with CRLs in PEM format
to use when verifying SSL/TLS server certificates.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-key
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.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
\fBssl-key-\fIuser\fB@\fIhost\fR
Sets an account-specific file name
for the private key of a SSL/TLS client certificate.
Overrides
.I ssl-key
for the specified account.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-method
Selects a SSL/TLS protocol version;
valid values are `ssl2', `ssl3', and `tls1'.
If unset, the method is selected automatically,
if possible.
.TP
\fBssl-method-\fIuser\fB@\fIhost\fR
Overrides
.I ssl-method
for a specific account.
.TP
.B ssl-rand-egd
Gives the pathname to an entropy daemon socket,
see
.IR RAND_egd (3).
.TP
.B ssl-rand-file
Gives the pathname to a file with entropy data,
see
.IR 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.
Only applicable if SSL/TLS support is built using OpenSSL.
.TP
.B ssl-verify
Sets the action to be performed if an error occurs
during SSL/TLS server certificate validation.
Valid values are
`strict' (fail and close connection immediately),
`ask' (ask whether to continue on standard input),
`warn' (print a warning and continue),
`ignore' (do not perform validation).
The default is `ask'.
.TP
\fBssl-verify-\fIuser\fB@\fIhost\fR
Overrides
.I ssl-verify
for a specific account.
.TP
.B stealthmua
If only set without a value assigned, then this option inhibits the
generation of the \fI`Message-Id:'\fR and \fI`User-Agent:'\fR
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 `noagent', then the mentioned \fI`Message-Id:'\fR
suppression doesn't occur.
.TP
.B 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.
.TP
.B ttycharset
The character set of the terminal \*(UA operates on.
There is normally no need to set this variable
since \*(UA can determine this automatically
by looking at the LC_CTYPE locale setting;
if this succeeds, the value is assigned at startup
and will be displayed by the \fIset\fP command.
Note that this is not necessarily a character set name
that can be used in Internet messages.
.TP
.B VISUAL
Pathname of the text editor to use
in the visual command and ~v escape.
.SH ENVIRONMENT VARIABLES
Besides the variables described above, \*(UA uses
the following environment strings:
.TP
.B HOME
The user's home directory.
.TP
\fBLANG\fR, \fBLC_ALL\fR, \fBLC_COLLATE\fR, \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR
See
.IR locale (7).
.TP
.B MAILRC
Is used as a startup file instead of \*(ur if set.
When \*(UA scripts are invoked on behalf of other users,
this variable should be set to `/dev/null' to avoid side-effects from
reading their configuration files.
.TP
.B NAILRC
If this variable is set and
.I MAILRC
is not set,
it is read as startup file.
.TP
.B SYSV3
Changes the letters printed in the first column of a header summary.
.TP
.B TMPDIR
Used as directory for temporary files instead of /tmp, if set.
.SH FILES
.TP
\*(ur
File giving initial commands.
.TP
\*(UR
System wide initialization file.
.TP
~/.mime.types
Personal MIME types.
.TP
/etc/mime.types
System wide MIME types.
.SH EXAMPLES
.SS "Getting started"
The \*(UA
command has two distinct usages, according to whether one
wants to send or receive mail.
Sending mail is simple: to send a
message to a user whose email address is, say,
<bill@host.example>,
use the shell
command:
.nf
.sp
    $ \*(ba\fI bill@host.example\fR
.sp
.fi
then type your message.
\*(UA will prompt you for a message
.I subject 
first;
after that, lines typed by you form the body of the message.
When you reach the end of the message, type
an EOT (control\-d) at the beginning of a line, which will cause
\*(UA to echo `EOT' and return you to the shell.
.PP
If, while you are composing the message
you decide that you do not wish to send it after all, you can
abort the letter with a \s-2RUBOUT\s0.  Typing a single \s-2RUBOUT\s0
causes \*(UA
to print `(Interrupt -- one more to kill letter)'.
Typing a second
\s-2RUBOUT\s0 causes \*(UA
to save your partial letter on the file `dead.letter'
in your home directory and abort the letter.
Once you have
sent mail to someone, there is no way to undo the act, so be
careful.
.PP
If you want to send the same message to several other people,
you can list their email addresses on the command line.
Thus,
.nf
.sp
    $ \*(ba\fI sam@workstation.example bob@server.example\fR
    Subject: Fees
    Tuition fees are due next Friday.  Don't forget!
    <Control\-d>
    EOT
    $
.sp
.fi
will send the reminder to \fI<sam@workstation.example>\fR.
and
\fI<bob@server.example>\fR.
.PP
To read your mail, simply type
.nf
.sp
    $ \*(ba
.sp
.fi
\*(UA
will respond by typing its version number and date and then listing
the messages you have waiting.
Then it will type a prompt and await your command.
The messages are assigned numbers starting with 1\(emyou
refer to the messages with these numbers.
\*(UA keeps track of which messages are
.I new
(have been sent since you last read your mail) and
.I read
(have been read by you).  New messages have an
.B N
next to them in the header listing and old, but unread messages have
a
.B U
next to them.
\*(UA keeps track of new/old and read/unread messages by putting a
header field called
.I Status
into your messages.
.PP
To look at a specific message, use the
.I type
command, which may be abbreviated to simply \fIt\fR.
For example, if you had the following messages:
.nf
.sp
    O 1 drfoo@myhost.example Wed Sep  1 19:52  18/631 "Fees"
    O 2 sam@friends.example  Thu Sep  2 00:08  30/895
.sp
.fi
you could examine the first message by giving the command:
.nf
.sp
    \fBtype\fR 1
.sp
.fi
which might cause \*(UA to respond with, for example:
.nf
.sp
    Message  1:
    From drfoo@myhost.example Wed Sep  1 19:52:25 2004
    Subject: Fees
    Status: R

    Tuition fees are due next Wednesday.  Don't forget!
.sp
.fi
.PP
Many \*(UA
commands that operate on messages take a message number as an
argument like the
.I type
command.
For these commands, there is a notion of a current message.
When you enter the \*(UA
program, the current message is initially the first
(or the first recent) one.
Thus, you can often omit the message number and use, for example,
.nf
.sp
    \fBt\fR
.sp
.fi
to type the current message.
As a further shorthand, you can type a message
by simply giving its message number.
Hence,
.nf
.sp
    1
.sp
.fi
would type the first message.
.PP
Frequently, it is useful to read the messages in your mailbox in order,
one after another.
You can read the next message in \*(UA
by simply typing a newline.
As a special case, you can type a newline as your first command to
\*(UA to type the first message.
.PP
If, after typing a message, you wish to immediately send a reply,
you can do so with the
.I reply
command.
This command,
like
.IR type ,
takes a message number as an argument.
\*(UA
then begins a message addressed to the user who sent you the message.
You may then type in your letter in reply, followed by a <control-d>
at the beginning of a line, as before.
.PP
Note that \*(UA
copies the subject header from the original message.
This is useful in that correspondence
about a particular matter will tend to retain the same subject heading,
making it easy to recognize.
If there are other header fields in the message,
like `Cc:',
the information found will also be used.
.PP
Sometimes you will receive a message that has been sent to
several people and wish to reply only
to the person who sent it.
.I Reply
with a capital
.I R
replies to a message, but sends a copy to the sender only.
.PP
If you wish, while reading your mail, to send a message to someone,
but not as a reply to one of your messages, you can send the message
directly with the
.I mail
command, which takes as arguments the names of the recipients you wish
to send to.
For example, to send a message to <frank@machine.example>,
you would do:
.nf
.sp
    \fBmail\fI frank@machine.example\fR
.fi
.PP
To delete a message from the mail folder,
you can use the
.I delete
command.
In addition to not saving deleted messages,
\*(UA will not let you type them, either.
The effect is to make the message disappear
altogether, along with its number.
.PP
Many features of \*(UA can be tailored to your liking with the
.I set
command.
The
.I set
command has two forms, depending on whether you are setting a
.I binary
option or a
.I valued
option.
Binary options are either on or off.  For example, the
.I askcc
option informs \*(UA
that each time you send a message, you want it to prompt you for
a `Cc:' header,
to be included in the message.
To set the
.I askcc
option, you would type
.nf
.sp
    \fBset\fR askcc
.fi
.PP
Valued options are values which \*(UA uses to adapt to your tastes.
For example, the
.I record
option tells \*(UA
where to save messages sent by you,
and is specified by
.nf
.sp
    \fBset\fR record=Sent
.sp
.fi
for example.
Note that no spaces are allowed in \fI"set record=Sent"\fR.
.PP
\*(UA includes a simple facility for maintaining groups of messages
together in folders.
To use the folder facility, you must tell \*(UA
where you wish to keep your folders.
Each folder of messages will be a single file.
For convenience, all of your folders are kept in
a single directory of your choosing.
To tell \*(UA where your folder directory is, put a line of the form
.nf
.sp
    \fBset folder=\fIletters\fR
.sp
.fi
in your \*(ur file.
If, as in the example above,
your folder directory does not begin with a `/',
\*(UA will assume that your folder directory is to be found starting
from your home directory.
.PP
Anywhere a file name is expected, you can use a folder name, preceded
with `+'.
For example, to put a message into a folder with the
.I save
command, you can use:
.nf
.sp
    \fBsave +\fIclasswork\fR
.sp
.fi
to save the current message in the
.I classwork
folder.
If the
.I classwork
folder does not yet exist, it will be created.
Note that messages which are saved with the
.I save
command are automatically removed from your system mailbox.
.PP
In order to make a copy of a message in a folder without causing
that message to be removed from your system mailbox, use the
.I copy
command, which is identical in all other respects to the
.I save
command.
.PP
The
.I folder
command
can be used to direct \*(UA to the contents of a different folder.
For example,
.nf
.sp
    \fBfolder +\fIclasswork\fR
.sp
.fi
directs \*(UA to read the contents of the
.I classwork
folder.
All of the commands that you can use on your system
mailbox are also applicable to folders, including
.IR type ,
.IR delete ,
and
.IR reply .
To inquire which folder you are currently editing, use simply:
.nf
.sp
    \fBfolder\fR
.fi
.PP
To list your current set of folders, use the
.I folders
command.
.PP
Finally, the
.I help
command is available to print out a brief summary of the most important
\*(UA commands.
.PP
While typing in a message to be sent to others, it is often
useful to be able to invoke the text editor on the partial message,
print the message, execute a shell command, or do some other
auxiliary function. 
\*(UA provides these capabilities through \fI"tilde escapes"\fR,
which consist of a tilde (~) at the beginning of a line, followed by
a single character which indicates the function to be performed.
For example, to print the text of the message so far, use:
.nf
.sp
    \fB~p\fR
.sp
.fi
which will print a line of dashes, the recipients of your message, and
the text of the message so far.
A list of the most important tilde escapes is available with `~?'.
.SS "IMAP or POP3 client setup"
First you need the following data from your ISP:
the host name of the IMAP or POP3 server,
user name and password for this server,
and a notice whether the server uses SSL/TLS encryption.
Assuming the host name is `server.myisp.example'
and your user name for that server is `mylogin',
you can refer to this account using the
.I folder
command or
.I \-f
command line option with
.nf

    \fBimaps://\fImylogin\fB@\fIserver.myisp.example\fR

.fi
(This string is not necessarily the same as your Internet mail address.)
You can replace `imaps://' with `imap://'
if the server does not support SSL/TLS.
(If SSL/TLS support is built using NSS, the
.I nss-config-dir
variable must be set before a connection can be initiated,
see above).
Use `pop3s://' or `pop3://' if the server does not offer IMAP.
You should use IMAP if you can, though;
first because it requires fewer network operations than POP3
to get the contents of the mailbox
and is thus faster;
and second because message attributes
are maintained by the IMAP server,
so you can easily distinguish new and old messages
each time you connect.
Even if the server does not accept IMAPS or POP3S connections,
it is possible that it supports the STARTTLS method
to make a session SSL/TLS encrypted
after the initial connection has been performed,
but before authentication begins.
The only reliable method to see if this works is to try it; enter one of
.nf

    \fBset imap-use-starttls\fR
    \fBset pop3-use-starttls\fR

.fi
before you initiate the connection.
.PP
As you probably want messages to be deleted from this account
after saving them,
prefix it with `\fI%:\fR'.
The
.I shortcut
command can be used to avoid typing that many characters
every time you want to connect:
.nf

    \fBshortcut \fImyisp\fB \fB%:imaps://\fImylogin\fB@\fIserver.myisp.example\fR

.fi
You might want to put this string into a startup file.
As the
.I shortcut
command is specific to this implementation of \*(UA and will confuse other
implementations, it should not be used in \*(ur, instead, put
.nf

    \fBset NAIL_EXTRA_RC=.\*(uarc

.fi
in \*(ur and create a file ~/.\*(uarc containing the
.I shortcut
command above.
You can then access your remote mailbox by invoking
`\*(ua \-f \fImyisp\fR' on the command line,
or by executing `fi \fImyisp\fR' within \*(UA.
.PP
If you want to use more than one IMAP mailbox on a server,
or if you want to use the IMAP server for mail storage too,
the
.I account
command
(which is also \*(UA-\fRspecific)
is more appropriate than the
.I shortcut
command.
You can put the following in
.IR ~/.\*(uarc :
.sp
.nf
    \fBaccount \fImyisp \fB{\fR
        \fBset folder=imaps://\fImylogin\fB@\fIserver.myisp.example\fR
        \fBset record=+\fISent \fBMBOX=+\fImbox \fBoutfolder\fR
    \fB}\fR
.fi
.sp
and can then access incoming mail for this account by invoking
`\*(ua \-A \fImyisp\fR' on the command line,
or by executing `ac \fImyisp\fR' within \*(UA.
After that,
a command like `copy \fI1\fR +\fIotherfolder\fR'
will refer to \fIotherfolder\fR on the IMAP server.
In particular,
`fi &' will change to the
.I mbox
folder,
and
`fi +Sent' will show your recorded sent mail,
with both folders located on the IMAP server.
.PP
\*(UA will ask you for a password string
each time you connect to a remote account.
If you can reasonably trust the security
of your workstation,
you can give this password in the startup file as
.nf

    \fBset password-\fImylogin\fB@\fIserver.myisp.example\fB="\fISECRET\fB"\fR

.fi
You should change the permissions of this file to 0600, see
.IR chmod (1).
.PP
\*(UA supports different authentication methods for both IMAP and POP3.
If Kerberos is used at your location,
you can try to activate GSSAPI-based authentication by
.nf

    \fBset imap-auth=gssapi\fR

.fi
The advantage of this method is that
\*(UA does not need to know your password at all,
nor needs to send sensitive data over the network.
Otherwise, the options
.nf

    \fBset imap-auth=cram-md5\fR
    \fBset pop3-use-apop\fR

.fi
for IMAP and POP3, respectively,
offer authentication methods
that avoid to send the password in clear text over the network,
which is especially important if SSL/TLS cannot be used.
If the server does not offer any of these authentication methods,
conventional user/password based authentication must be used.
It is sometimes helpful to set the
.I verbose
option when authentication problems occur.
\*(UA will display all data sent to the server in clear text on the
screen with this option,
including passwords.
You should thus take care that no unauthorized person
can look at your terminal when this option is set.
.PP
If you regularly use the same workstation
to access IMAP accounts,
you can greatly enhance performance
by enabling local caching of IMAP messages.
For any message that has been fully or partially fetched from the server,
a local copy is made and is used when the message is accessed again,
so most data is transferred over the network once only.
To enable the IMAP cache,
select a local directory name and put
.nf

    \fBset imap-cache=\fI~/localdirectory\fR

.fi
in the startup file.
All files within that directory
can be overwritten or deleted by \*(UA at any time,
so you should not use the directory to store other information.
.PP
Once the cache contains some messages,
it is not strictly necessary anymore
to open a connection to the IMAP server
to access them.
When \*(UA is invoked with the \fI\-D\fR option,
or when the
.I disconnected
variable is set,
only cached data is used
for any folder you open.
Messages that have not yet been completely cached
are not available then,
but all other messages can be handled
as usual.
Changes made to IMAP mailboxes in
.I disconnected
mode are committed to the IMAP server
next time it is used in
.I online
mode.
Synchronizing the local status
with the status on the server
is thus partially within your responsibility;
if you forget to initiate a connection to the server again
before you leave your location,
changes made on one workstation
are not available on others.
Also if you alter IMAP mailboxes from a workstation
while uncommitted changes are still pending on another,
the latter data may become invalid.
The same might also happen because of internal server status changes.
You should thus carefully evaluate this feature in your environment
before you rely on it.
.PP
Many servers will close the connection
after a short period of inactivity. Use one of
.nf

    \fBset pop3-keepalive=\fI30\fR
    \fBset imap-keepalive=\fI240\fR

.fi
to send a keepalive message each 30 seconds for POP3,
or each 4 minutes for IMAP.
.PP
If you encounter problems connecting to a SSL/TLS server,
try the
.I ssl-rand-egd
and
.I ssl-rand-file
variables (see the OpenSSL FAQ for more information)
or specify the protocol version with
.IR ssl-method .
Contact your ISP
if you need a client certificate
or if verification of the server certificate fails.
If the failed certificate is indeed valid,
fetch its CA certificate by executing the shell command
.nf

    $ \fBopenssl s_client </dev/null \-showcerts \-connect \e
        \fIserver.myisp.example\fB:\fIimaps\fB 2>&1 | tee \fIlog\fR

.fi
(see
.IR s_client (1))
and put it into the file specified with
.IR ssl-ca-file .
The data you need is located at the end of the certificate chain
within (and including) the `BEGIN CERTIFICATE'
and `END CERTIFICATE' lines.
Note that the example above is \fIinsecure\fR!
One should use the `-verify' and `-CAfile' options of
.IR s_client (1)
to be "on the safe side" regarding the fetched certificates.
.SS "Creating a score file or message filter"
The scoring commands are best separated
from other configuration for clarity,
and are mostly \*(UA specific.
It is thus recommended to put them in a separate file
that is sourced from your NAIL_EXTRA_RC as follows:
.nf
.sp
    \fBsource\fI ~/.scores\fR
.sp
.fi
The \fI.scores\fR file could then look as follows:
.nf
.sp
    \fBdefine\fR \fIlist\fR {
        \fBscore\fR (subject "important discussion") +10
        \fBscore\fR (subject "annoying discussion") \-10
        \fBscore\fR (from "nicefellow@goodnet") +15
        \fBscore\fR (from "badguy@poornet") \-5
        \fBmove\fR (header x-spam-flag "+++++") \fI+junk\fR
    }
    \fBset folder-hook-\fRimap://user@host/public.list=\fIlist\fR
.sp
.fi
In this scheme,
you would see any mail from `nicefellow@goodnet',
even if the surrounding discussion is annoying;
but you normally would not see mail from `badguy@poornet',
unless he participates in the important discussion.
Messages that are marked with five or more plus characters
in their `X-Spam-Flag' field
(inserted by some server-side filtering software)
are moved to the folder `junk' in the
.I folder
directory.
.PP
Be aware that all criteria in (\|) lead to substring matches,
so you would also score messages
from e.\|g. `notsobadguy@poornetmakers' negative here.
It is possible to select addresses exactly using \fI"address"\fR
message specifications,
but these cannot be executed remotely 
and will thus cause all headers
to be downloaded from IMAP servers while looking for matches.
.PP
When searching messages on an IMAP server,
best performance is usually achieved
by sending as many criteria as possible
in one large (\|) specification,
because each single such specification
will result in a separate network operation.
.SS "Activating the Bayesian filter"
The Bayesian junk mail filter works
by examining the words contained in messages.
You decide yourself what a good and what a bad message is.
Thus the resulting filter is your very personal one;
once it is correctly set up,
it will filter only messages similar to those
previously specified by you.
.PP
To use the Bayesian filter,
a location for the junk mail database must be defined first:
.nf
.sp
    \fBset junkdb=\fI~/.junkdb\fR
.sp
.fi
The junk mail database does not contain
actual words extracted from messages,
but hashed representations of them.
A foreign person who can read the database
could only examine the frequency of previously known words
in your mail.
.PP
If you have sufficient disk space (several 10\ MB) available,
it is recommended that you set the
.I chained-junk-tokens
option.
The filter will then also consider two-word tokens,
improving its accuracy.
.PP
A set of good messages and junk messages must now be available;
it is also possible to use the incoming new messages for this purpose,
although it will of course take some time
until the filter becomes useful then.
Do not underestimate the amount of statistical data needed;
some hundred messages are typically necessary
to get satisfactory results,
and many thousand messages for best operation.
You have to pass the good messages to the
.I good
command,
and the junk messages to the
.I junk
command.
If you ever accidentally mark a good message as junk or vice-versa,
call the
.I ungood
or
.I unjunk
command to correct this.
.PP
Once a reasonable amount of statistics has been collected,
new messages can be classified automatically.
The
.I classify
command marks all messages that the filter considers to be junk,
but it does not perform any action on them by default.
It is recommended that you move these messages into a separate
folder just for the case that false positives occur,
or to pass them to the
.I junk
command later again to further improve the junk mail database.
To automatically move incoming junk messages
every time the inbox is opened,
put lines like the following into your
.I .scores
file (or whatever name you gave to the file in the last example):
.nf
.sp
    \fBdefine\fR \fIjunkfilter\fR {
        \fBclassify (smaller \fI20000\fB) :n\fR
        \fBmove :j\fR \fI+junk\fR
    }
    \fBset folder-hook-\fRimap://user@host/INBOX=\fIjunkfilter\fR
.sp
.fi
If you set the
.I verbose
option before running the
.I classify
command,
\*(UA prints the words it uses for calculating the junk status
along with their statistical probabilities.
This can help you to find out
why some messages are not classified
as you would like them to be.
To see the statistical probability of a given word,
use the
.I probability
command.
.PP
If a junk message was not recognized as such,
use the
.I junk
command to correct this.
Also if you encounter a false positive
(a good message that was wrongly classified as junk),
pass it to the
.I good
command.
.PP
Since the
.I classify
command must examine the entire text
of all new messages in the respective folder,
this will also cause all of them to be downloaded from the IMAP server.
You should thus restrict the size of messages for automatic filtering.
If server-based filtering is also available,
you might try if that works for you first.
.SS "Reading HTML mail"
You need either the
.I w3m
or
.I lynx
utility
or another command-line web browser
that can write plain text to standard output.
.nf
.sp
    \fBset pipe-text/html=\fR"w3m -dump -T text/html"
.sp
.fi
or
.nf
.sp
    \fBset pipe-text/html=\fR"lynx -dump -force_html /dev/stdin"
.sp
.fi
will then cause HTML message parts to be converted into a more friendly form.
.SS "Viewing PDF attachments"
Most PDF viewers do not accept input directly from a pipe.
It is thus necessary to store the attachment in a temporary file, as with
.nf
.sp
    \fBset pipe-application/pdf=\fR"cat >/tmp/\*(ua$$.pdf; \e
        acroread /tmp/\*(ua$$.pdf; rm /tmp/\*(ua$$.pdf"
.sp
.fi
Note that security defects are discovered in PDF viewers
from time to time.
Automatical command execution like this
can compromise your system security,
in particular if you stay not always informed
about such issues.
.SS "Signed and encrypted messages with S/MIME"
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.
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 thus 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.
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,
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.)
You will usually receive
a combined certificate and private key
in PKCS#12 format which
\*(UA does not directly accept
if S/MIME support is built using OpenSSL.
To convert it to PEM format,
use the following shell command:
.nf
.sp
    $ \fBopenssl pkcs12 \-in \fIcert.p12\fB \-out \fIcert.pem\fB \-clcerts \e
        \-nodes\fR
.sp
.fi
If you omit the
.I \-nodes
parameter,
you can specifiy an additional
.I "PEM pass phrase"
for protecting the private key.
\*(UA will then ask you for that pass phrase
each time it signs or decrypts a message.
You can then use
.nf
.sp
    \fBset smime-sign-cert-\fImyname@myisp.example\fB=\fIcert.pem\fR
.sp
.fi
to make this private key and certificate known to \*(UA.
.PP
If S/MIME support is built using NSS,
the PKCS#12 file must be installed using Mozilla
(provided that
.I nss-config-dir
is set appropriately,
see above),
and no further action is necessary
unless multiple user certificates
for the same email address are installed.
In this case,
the
.I smime-sign-nickname
variable has to be set appropriately.
.PP
You can now sign outgoing messages.
Just use
.nf
.sp
    \fBset smime-sign\fR
.sp
.fi
to do so.
.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.
First use the
.I verify
command to check the validity of the certificate.
After that,
retrieve the certificate and tell
\*(UA that it should use it for encryption:
.nf
.sp
    \fBcertsave\fI filename\fR
    \fBset smime-encrypt-\fIuser@host\fB=\fIfilename\fR
.sp
.fi
If S/MIME support is built using NSS,
the saved certificate must be installed using Mozilla.
The value of the
.I smime-encrypt-user@host
is ignored then,
but if multiple certificates for the recipient are available,
the
.I smime-nickname-user@host
variable must be set.
.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
.I decrypt
command saves messages in decrypted form,
while the
.IR save ,
.IR copy ,
and
.I move
commands leave them encrypted.
.PP
Note that neither S/MIME signing nor encryption
applies to message subjects or other header fields.
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"
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,
or to access them on the Internet,
so you have to retrieve them by some external mechanism.
.PP
If S/MIME and SSL/TLS support are built using OpenSSL,
\*(UA accepts CRLs in PEM format only;
CRLs in DER format must be converted,
e.\|g. with the shell command
.nf
.sp
    $ \fBopenssl crl \-inform DER \-in \fIcrl.der\fB \-out \fIcrl.pem\fR
.sp
.fi
To tell \*(UA about the CRLs,
a directory
that contains all CRL files
(and no other files)
must be created.
The
.I smime-crl-dir
or
.I 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.
.PP
If S/MIME and SSL/TLS support are built using NSS,
CRLs can be imported in Mozilla applications
(provided that
.I nss-config-dir
is set appropriately).
.SS "Sending mail from scripts"
If you want to send mail from scripts,
you must be aware that
\*(UA reads the user's configuration files by default.
So unless your script is only intended for your own personal use
(as e.g. a cron job),
you need to circumvent this by invoking \*(UA like
.nf
.sp
    \fBMAILRC=/dev/null \*(ua \-n\fR
.sp
.fi
You then need to create a configuration for \*(UA for your script.
This can be done by either pointing the
.I MAILRC
variable to a custom configuration file,
or by passing the configuration in environment variables.
Since many of the configuration options are not valid shell variables, the
.I env
command is useful in this situation.
An invocation could thus look like
.nf
.sp
    \fBenv MAILRC=/dev/null\fR from=\fIscriptreply@domain\fR smtp=\fIhost\fR \e
        smtp-auth-user=\fIlogin\fR smtp-auth-password=\fIsecret\fR \e
        smtp-auth=\fIlogin\fR \*(ba\fB \-n\fR \-s "\fIsubject\fR" \e
        \-a \fIattachment_file\fR \fIrecipient@domain\fR <\fIcontent_file\fR
.SH "SEE ALSO"
fmt(1),
more(1),
newaliases(1),
openssl(1),
pg(1),
sendmail(1)
vacation(1),
ssl(3),
aliases(5),
locale(7),
mailaddr(7)
.SH NOTES
.PP
Variables in the environment passed to \*(UA cannot be unset.
.PP
The character set conversion relies
on the
.IR iconv (3)
function.
Its functionality differs widely
between the various system environments \*(UA runs on.
If the message `Cannot convert from \fIa\fR to \fIb\fR' appears,
either some characters within the message header or text
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 LC_CTYPE locale (e.\|g. \fIen_US\fR)
or the
.I ttycharset
variable.
In the second case, the
.I sendcharsets
and
.I ttycharset
variables must be set to the same value
to inhibit character set conversion.
If
.I iconv()
is not available at all,
the value assigned to
.I sendcharsets
must match the character set that is used on the terminal.
.PP
\*(UA expects input text to be in Unix format,
with lines separated by 
.I newline
(^J, \en) characters only.
Non-Unix text files that use
.I carriage return
(^M, \er)
characters in addition will be treated as binary data;
to send such files as text, strip these characters e.\ g. by
.sp
    $ tr \-d '\e015' <input | \*(ua .\ .\ .
.sp
.RE
or fix the tools that generate them.
.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
.I exit
command instead of
.I quit
will not cause it to be reset,
and if the
.IR autoinc / newmail
variables are 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.
.\" This is why \*(UA does not even check if storing them succeeds.
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 \fIn\fR 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 `exit' command will not cause the message status to be reset.
The `newmail' command and the `newmail' variable
have no effect.
It is not possible to rename or to remove POP3 mailboxes.
.PP
If a
.SM RUBOUT
(interrupt) 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
.I 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 the connection is no longer usable.
.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 a `dead.letter' file.
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 \fIsendmail(1)\fR)
even when operating in
.I 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
.I 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.
.PP
The junk mail filter follows the concepts developed by
Paul Graham in his articles,
``A Plan for Spam'', August 2002,
\%<http://www.paulgraham.com/spam.html>,
and ``Better Bayesian Filtering'', January 2003,
\%<http://www.paulgraham.com/better.html>.
Chained tokens are due to a paper by
Jonathan A. Zdziarski,
``Advanced Language Classification using Chained Tokens'',
February 2004,
\%<http://www.nuclearelephant.com/papers/chained.html>.
.PP
A \fImail\fR command appeared in Version 1 AT&T Unix.
Berkeley Mail was written in 1978 by Kurt Shoens.
This man page is derived from
from The Mail Reference Manual
originally written by Kurt Shoens.
\fIHeirloom Mailx\fR enhancements are maintained and documented
by Gunnar Ritter.
\fIS-nail\fR enhancements are 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
\(em 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
\%<http://www.opengroup.org/unix/online.html>.
Redistribution of this material is permitted so long as this notice remains
intact.