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;;; smtpmail.el --- simple SMTP protocol (RFC 821) for sending mail

;; Copyright (C) 1995-1996, 2001-2014 Free Software Foundation, Inc.

;; Author: Tomoji Kagatani <kagatani@rbc.ncl.omron.co.jp>
;; Maintainer: Simon Josefsson <simon@josefsson.org>
;; w32 Maintainer: Brian D. Carlstrom <bdc@ai.mit.edu>
;; ESMTP support: Simon Leinen <simon@switch.ch>
;; Hacked by Mike Taylor, 11th October 1999 to add support for
;; automatically appending a domain to RCPT TO: addresses.
;; AUTH=LOGIN support: Stephen Cranefield <scranefield@infoscience.otago.ac.nz>
;; Keywords: mail

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Send Mail to smtp host from smtpmail temp buffer.

;; Please add these lines in your .emacs(_emacs) or use customize.
;;
;;(setq send-mail-function 'smtpmail-send-it) ; if you use `mail'
;;(setq message-send-mail-function 'smtpmail-send-it) ; if you use message/Gnus
;;(setq smtpmail-smtp-server "YOUR SMTP HOST")
;;(setq smtpmail-local-domain "YOUR DOMAIN NAME")
;;(setq smtpmail-sendto-domain "YOUR DOMAIN NAME")
;;(setq smtpmail-debug-info t) ; only to debug problems

;; To queue mail, set `smtpmail-queue-mail' to t and use
;; `smtpmail-send-queued-mail' to send.

;; Modified by Stephen Cranefield <scranefield@infoscience.otago.ac.nz>,
;; 22/6/99, to support SMTP Authentication by the AUTH=LOGIN mechanism.
;; See http://help.netscape.com/products/server/messaging/3x/info/smtpauth.html
;; Rewritten by Simon Josefsson to use same credential variable as AUTH
;; support below.

;; Modified by Simon Josefsson <jas@pdc.kth.se>, 22/2/99, to support SMTP
;; Authentication by the AUTH mechanism.
;; See http://www.ietf.org/rfc/rfc2554.txt

;;; Code:

(require 'sendmail)
(require 'auth-source)
(autoload 'mail-strip-quoted-names "mail-utils")
(autoload 'message-make-date "message")
(autoload 'message-make-message-id "message")
(autoload 'rfc2104-hash "rfc2104")

;;;
(defgroup smtpmail nil
  "SMTP protocol for sending mail."
  :group 'mail)


(defcustom smtpmail-default-smtp-server nil
  "Specify default SMTP server.
This only has effect if you specify it before loading the smtpmail library."
  :type '(choice (const nil) string)
  :group 'smtpmail)

(defcustom smtpmail-smtp-server
  (or (getenv "SMTPSERVER") smtpmail-default-smtp-server)
  "The name of the host running SMTP server."
  :type '(choice (const nil) string)
  :group 'smtpmail)

(defcustom smtpmail-smtp-service 25
  "SMTP service port number.
The default value would be \"smtp\" or 25."
  :type '(choice (integer :tag "Port") (string :tag "Service"))
  :group 'smtpmail)

(defcustom smtpmail-smtp-user nil
  "User name to use when looking up credentials in the authinfo file.
If non-nil, only consider credentials for the specified user."
  :version "24.1"
  :type '(choice (const nil) string)
  :group 'smtpmail)

(defcustom smtpmail-local-domain nil
  "Local domain name without a host name.
If the function `system-name' returns the full internet address,
don't define this value."
  :type '(choice (const nil) string)
  :group 'smtpmail)

(defcustom smtpmail-stream-type nil
  "Type of SMTP connections to use.
This may be either nil (possibly upgraded to STARTTLS if possible),
or `starttls' (refuse to send if STARTTLS isn't available), or `plain'
\(never use STARTTLS), or `ssl' (to use TLS/SSL)."
  :version "24.1"
  :group 'smtpmail
  :type '(choice (const :tag "Possibly upgrade to STARTTLS" nil)
                 (const :tag "Always use STARTTLS" starttls)
                 (const :tag "Never use STARTTLS" plain)
                 (const :tag "Use TLS/SSL" ssl)))

(defcustom smtpmail-sendto-domain nil
  "Local domain name without a host name.
This is appended (with an @-sign) to any specified recipients which do
not include an @-sign, so that each RCPT TO address is fully qualified.
\(Some configurations of sendmail require this.)

Don't bother to set this unless you have get an error like:
        Sending failed; 501 <someone>: recipient address must contain a domain."
  :type '(choice (const nil) string)
  :group 'smtpmail)

(defcustom smtpmail-debug-info nil
  "Whether to print info in buffer *trace of SMTP session to <somewhere>*.
See also `smtpmail-debug-verb' which determines if the SMTP protocol should
be verbose as well."
  :type 'boolean
  :group 'smtpmail)

(defcustom smtpmail-debug-verb nil
  "Whether this library sends the SMTP VERB command or not.
The commands enables verbose information from the SMTP server."
  :type 'boolean
  :group 'smtpmail)

(defcustom smtpmail-code-conv-from nil
  "Coding system for encoding outgoing mail.
Used for the value of `sendmail-coding-system' when
`select-message-coding-system' is called. "
  :type 'coding-system
  :group 'smtpmail)

(defcustom smtpmail-queue-mail nil
  "Non-nil means mail is queued; otherwise it is sent immediately.
If queued, it is stored in the directory `smtpmail-queue-dir'
and sent with `smtpmail-send-queued-mail'."
  :type 'boolean
  :group 'smtpmail)

(defcustom smtpmail-queue-dir "~/Mail/queued-mail/"
  "Directory where `smtpmail.el' stores queued mail."
  :type 'directory
  :group 'smtpmail)

(defcustom smtpmail-warn-about-unknown-extensions nil
  "If set, print warnings about unknown SMTP extensions.
This is mainly useful for development purposes, to learn about
new SMTP extensions that might be useful to support."
  :type 'boolean
  :version "21.1"
  :group 'smtpmail)

(defcustom smtpmail-queue-index-file "index"
  "File name of queued mail index.
This is relative to `smtpmail-queue-dir'."
  :type 'string
  :group 'smtpmail)

;; End of customizable variables.


(defvar smtpmail-address-buffer)
(defvar smtpmail-recipient-address-list)

(defvar smtpmail-queue-counter 0)

;; Buffer-local variable.
(defvar smtpmail-read-point)

(defconst smtpmail-auth-supported '(cram-md5 plain login)
  "List of supported SMTP AUTH mechanisms.
The list is in preference order.")

(defvar smtpmail-mail-address nil
  "Value to use for envelope-from address for mail from ambient buffer.")

;;;###autoload
(defun smtpmail-send-it ()
  (let ((errbuf (if mail-interactive
                    (generate-new-buffer " smtpmail errors")
                  0))
        (tembuf (generate-new-buffer " smtpmail temp"))
        (case-fold-search nil)
        delimline
        result
        (mailbuf (current-buffer))
        ;; Examine this variable now, so that
        ;; local binding in the mail buffer will take effect.
        (smtpmail-mail-address
         (or (and mail-specify-envelope-from (mail-envelope-from))
             (let ((from (mail-fetch-field "from")))
               (and from
                    (cadr (mail-extract-address-components from))))
             (smtpmail-user-mail-address)))
        (smtpmail-code-conv-from
         (if enable-multibyte-characters
             (let ((sendmail-coding-system smtpmail-code-conv-from))
               (select-message-coding-system)))))
    (unwind-protect
        (with-current-buffer tembuf
          (erase-buffer)
          ;; Use the same `buffer-file-coding-system' as in the mail
          ;; buffer, otherwise any `write-region' invocations (e.g., in
          ;; mail-do-fcc below) will annoy with asking for a suitable
          ;; encoding.
          (set-buffer-file-coding-system smtpmail-code-conv-from nil t)
          (insert-buffer-substring mailbuf)
          (goto-char (point-max))
          ;; require one newline at the end.
          (or (= (preceding-char) ?\n)
              (insert ?\n))
          ;; Change header-delimiter to be what sendmail expects.
          (mail-sendmail-undelimit-header)
          (setq delimline (point-marker))
          ;; (sendmail-synch-aliases)
          (if mail-aliases
              (expand-mail-aliases (point-min) delimline))
          (goto-char (point-min))
          ;; ignore any blank lines in the header
          (while (and (re-search-forward "\n\n\n*" delimline t)
                      (< (point) delimline))
            (replace-match "\n"))
          (let ((case-fold-search t))
            ;; We used to process Resent-... headers here,
            ;; but it was not done properly, and the job
            ;; is done correctly in `smtpmail-deduce-address-list'.
            ;; Don't send out a blank subject line
            (goto-char (point-min))
            (if (re-search-forward "^Subject:\\([ \t]*\n\\)+\\b" delimline t)
                (replace-match "")
              ;; This one matches a Subject just before the header delimiter.
              (if (and (re-search-forward "^Subject:\\([ \t]*\n\\)+" delimline t)
                       (= (match-end 0) delimline))
                  (replace-match "")))
            ;; Put the "From:" field in unless for some odd reason
            ;; they put one in themselves.
            (goto-char (point-min))
            (if (not (re-search-forward "^From:" delimline t))
                (let* ((login smtpmail-mail-address)
                       (fullname (user-full-name)))
                  (cond ((eq mail-from-style 'angles)
                         (insert "From: " fullname)
                         (let ((fullname-start (+ (point-min) 6))
                               (fullname-end (point-marker)))
                           (goto-char fullname-start)
                           ;; Look for a character that cannot appear unquoted
                           ;; according to RFC 822.
                           (if (re-search-forward "[^- !#-'*+/-9=?A-Z^-~]"
                                                  fullname-end 1)
                               (progn
                                 ;; Quote fullname, escaping specials.
                                 (goto-char fullname-start)
                                 (insert "\"")
                                 (while (re-search-forward "[\"\\]"
                                                           fullname-end 1)
                                   (replace-match "\\\\\\&" t))
                                 (insert "\""))))
                         (insert " <" login ">\n"))
                        ((eq mail-from-style 'parens)
                         (insert "From: " login " (")
                         (let ((fullname-start (point)))
                           (insert fullname)
                           (let ((fullname-end (point-marker)))
                             (goto-char fullname-start)
                             ;; RFC 822 says \ and nonmatching parentheses
                             ;; must be escaped in comments.
                             ;; Escape every instance of ()\ ...
                             (while (re-search-forward "[()\\]" fullname-end 1)
                               (replace-match "\\\\\\&" t))
                             ;; ... then undo escaping of matching parentheses,
                             ;; including matching nested parentheses.
                             (goto-char fullname-start)
                             (while (re-search-forward
                                     "\\(\\=\\|[^\\]\\(\\\\\\\\\\)*\\)\\\\(\\(\\([^\\]\\|\\\\\\\\\\)*\\)\\\\)"
                                     fullname-end 1)
                               (replace-match "\\1(\\3)" t)
                               (goto-char fullname-start))))
                         (insert ")\n"))
                        ((null mail-from-style)
                         (insert "From: " login "\n")))))
            ;; Insert a `Message-Id:' field if there isn't one yet.
            (goto-char (point-min))
            (unless (re-search-forward "^Message-Id:" delimline t)
              (insert "Message-Id: " (message-make-message-id) "\n"))
            ;; Insert a `Date:' field if there isn't one yet.
            (goto-char (point-min))
            (unless (re-search-forward "^Date:" delimline t)
              (insert "Date: " (message-make-date) "\n"))
            ;; Possibly add a MIME header for the current coding system
            (let (charset)
              (goto-char (point-min))
              (and (eq mail-send-nonascii 'mime)
                   (not (re-search-forward "^MIME-version:" delimline t))
                   (progn (skip-chars-forward "\0-\177")
                          (/= (point) (point-max)))
                   smtpmail-code-conv-from
                   (setq charset
                         (coding-system-get smtpmail-code-conv-from
                                            'mime-charset))
                   (goto-char delimline)
                   (insert "MIME-version: 1.0\n"
                           "Content-type: text/plain; charset="
                           (symbol-name charset)
                           "\nContent-Transfer-Encoding: 8bit\n")))
            ;; Insert an extra newline if we need it to work around
            ;; Sun's bug that swallows newlines.
            (goto-char (1+ delimline))
            (if (eval mail-mailer-swallows-blank-line)
                (newline))
            ;; Find and handle any FCC fields.
            (goto-char (point-min))
            (if (re-search-forward "^FCC:" delimline t)
                ;; Force `mail-do-fcc' to use the encoding of the mail
                ;; buffer to encode outgoing messages on FCC files.
                (let ((coding-system-for-write
                       ;; mbox files must have Unix EOLs.
                       (coding-system-change-eol-conversion
                        smtpmail-code-conv-from 'unix)))
                  (mail-do-fcc delimline)))
            (if mail-interactive
                (with-current-buffer errbuf
                  (erase-buffer))))
          ;; Encode the header according to RFC2047.
          (mail-encode-header (point-min) delimline)
          ;;
          (setq smtpmail-address-buffer (generate-new-buffer "*smtp-mail*"))
          (setq smtpmail-recipient-address-list
                (smtpmail-deduce-address-list tembuf (point-min) delimline))
          (kill-buffer smtpmail-address-buffer)

          (smtpmail-do-bcc delimline)
          ;; Send or queue
          (if (not smtpmail-queue-mail)
              (if (not (null smtpmail-recipient-address-list))
                  (when (setq result
                              (smtpmail-via-smtp
                               smtpmail-recipient-address-list tembuf))
                    (error "Sending failed: %s" result))
                (error "Sending failed; no recipients"))
            (let* ((file-data
                    (expand-file-name
                     (format "%s_%i"
                             (format-time-string "%Y-%m-%d_%H:%M:%S")
                             (setq smtpmail-queue-counter
                                   (1+ smtpmail-queue-counter)))
                     smtpmail-queue-dir))
                   (file-data (convert-standard-filename file-data))
                   (file-elisp (concat file-data ".el"))
                   (buffer-data (create-file-buffer file-data))
                   (buffer-elisp (create-file-buffer file-elisp))
                   (buffer-scratch "*queue-mail*"))
              (unless (file-exists-p smtpmail-queue-dir)
                (make-directory smtpmail-queue-dir t))
              (with-current-buffer buffer-data
                (erase-buffer)
                (set-buffer-file-coding-system
                 ;; We will be reading the file with no-conversion in
                 ;; smtpmail-send-queued-mail below, so write it out
                 ;; with Unix EOLs.
                 (coding-system-change-eol-conversion
                  (or smtpmail-code-conv-from 'undecided)
                  'unix)
                 nil t)
                (insert-buffer-substring tembuf)
                (write-file file-data)
                (set-buffer buffer-elisp)
                (erase-buffer)
                (insert (concat
                         "(setq smtpmail-recipient-address-list '"
                         (prin1-to-string smtpmail-recipient-address-list)
                         ")\n"))
                (write-file file-elisp)
                (set-buffer (generate-new-buffer buffer-scratch))
                (insert (concat file-data "\n"))
                (append-to-file (point-min)
                                (point-max)
                                (expand-file-name smtpmail-queue-index-file
                                                  smtpmail-queue-dir)))
              (kill-buffer buffer-scratch)
              (kill-buffer buffer-data)
              (kill-buffer buffer-elisp))))
      (kill-buffer tembuf)
      (if (bufferp errbuf)
          (kill-buffer errbuf)))))

;;;###autoload
(defun smtpmail-send-queued-mail ()
  "Send mail that was queued as a result of setting `smtpmail-queue-mail'."
  (interactive)
  (with-temp-buffer
    ;; Get index, get first mail, send it, update index, get second
    ;; mail, send it, etc...
    (let ((file-msg "")
          (qfile (expand-file-name smtpmail-queue-index-file
                                   smtpmail-queue-dir))
          result)
      (insert-file-contents qfile)
      (goto-char (point-min))
      (while (not (eobp))
        (setq file-msg (buffer-substring (point) (line-end-position)))
        (load file-msg)
        ;; Insert the message literally: it is already encoded as per
        ;; the MIME headers, and code conversions might guess the
        ;; encoding wrongly.
        (with-temp-buffer
          (let ((coding-system-for-read 'no-conversion))
            (insert-file-contents file-msg))
          (let ((smtpmail-mail-address
                 (or (and mail-specify-envelope-from (mail-envelope-from))
                     user-mail-address)))
            (if (not (null smtpmail-recipient-address-list))
                (when (setq result (smtpmail-via-smtp
                                    smtpmail-recipient-address-list
                                    (current-buffer)))
                  (error "Sending failed: %s" result))
              (error "Sending failed; no recipients"))))
        (delete-file file-msg)
        (delete-file (concat file-msg ".el"))
        (delete-region (point-at-bol) (point-at-bol 2)))
      (write-region (point-min) (point-max) qfile))))

(defun smtpmail-fqdn ()
  (if smtpmail-local-domain
      (concat (system-name) "." smtpmail-local-domain)
    (system-name)))

(defsubst smtpmail-cred-server (cred)
  (nth 0 cred))

(defsubst smtpmail-cred-port (cred)
  (nth 1 cred))

(defsubst smtpmail-cred-key (cred)
  (nth 2 cred))

(defsubst smtpmail-cred-user (cred)
  (nth 2 cred))

(defsubst smtpmail-cred-cert (cred)
  (nth 3 cred))

(defsubst smtpmail-cred-passwd (cred)
  (nth 3 cred))

(defun smtpmail-find-credentials (cred server port)
  (catch 'done
    (let ((l cred) el)
      (while (setq el (pop l))
        (when (and (equal server (smtpmail-cred-server el))
                   (equal port (smtpmail-cred-port el)))
          (throw 'done el))))))

(defun smtpmail-maybe-append-domain (recipient)
  (if (or (not smtpmail-sendto-domain)
          (string-match "@" recipient))
      recipient
    (concat recipient "@" smtpmail-sendto-domain)))

(defun smtpmail-intersection (list1 list2)
  (let ((result nil))
    (dolist (el2 list2)
      (when (memq el2 list1)
        (push el2 result)))
    (nreverse result)))

(defun smtpmail-command-or-throw (process string &optional code)
  (let (ret)
    (smtpmail-send-command process string)
    (unless (smtpmail-ok-p (setq ret (smtpmail-read-response process))
                           code)
      (throw 'done (format "%s in response to %s"
                           (smtpmail-response-text ret)
                           string)))
    ret))

(defun smtpmail-try-auth-methods (process supported-extensions host port
                                          &optional ask-for-password)
  (setq port
        (if port
            (format "%s" port)
          "smtp"))
  (let* ((mechs (cdr-safe (assoc 'auth supported-extensions)))
         (mech (car (smtpmail-intersection mechs smtpmail-auth-supported)))
         (auth-source-creation-prompts
          '((user  . "SMTP user name for %h: ")
            (secret . "SMTP password for %u@%h: ")))
         (auth-info (car
                     (auth-source-search
                      :host host
                      :port port
                      :user smtpmail-smtp-user
                      :max 1
                      :require (and ask-for-password
                                    '(:user :secret))
                      :create ask-for-password)))
         (user (plist-get auth-info :user))
         (password (plist-get auth-info :secret))
         (save-function (and ask-for-password
                             (plist-get auth-info :save-function)))
         ret)
    (when (functionp password)
      (setq password (funcall password)))
    (when (and user
               (not password))
      ;; The user has stored the user name, but not the password, so
      ;; ask for the password, even if we're not forcing that through
      ;; `ask-for-password'.
      (setq auth-info
            (car
             (auth-source-search
              :max 1
              :host host
              :port port
              :user smtpmail-smtp-user
              :require '(:user :secret)
              :create t))
            password (plist-get auth-info :secret)))
    (when (functionp password)
      (setq password (funcall password)))
    (let ((result (catch 'done
                    (smtpmail-try-auth-method process mech user password))))
      (if (stringp result)
          (progn
            (auth-source-forget+ :host host :port port)
            (throw 'done result))
        (when save-function
          (funcall save-function))
        result))))

(defun smtpmail-try-auth-method (process mech user password)
  (let (ret)
    (cond
     ((or (not mech)
          (not user)
          (not password))
      ;; No mechanism, or no credentials.
      mech)
     ((eq mech 'cram-md5)
      (setq ret (smtpmail-command-or-throw process "AUTH CRAM-MD5"))
      (when (eq (car ret) 334)
        (let* ((challenge (substring (cadr ret) 4))
               (decoded (base64-decode-string challenge))
               (hash (rfc2104-hash 'md5 64 16 password decoded))
               (response (concat user " " hash))
               ;; Osamu Yamane <yamane@green.ocn.ne.jp>:
               ;; SMTP auth fails because the SMTP server identifies
               ;; only the first part of the string (delimited by
               ;; new line characters) as a response from the
               ;; client, and the rest as distinct commands.

               ;; In my case, the response string is 80 characters
               ;; long.  Without the no-line-break option for
               ;; `base64-encode-string', only the first 76 characters
               ;; are taken as a response to the server, and the
               ;; authentication fails.
               (encoded (base64-encode-string response t)))
          (smtpmail-command-or-throw process encoded))))
     ((eq mech 'login)
      (smtpmail-command-or-throw process "AUTH LOGIN")
      (smtpmail-command-or-throw process (base64-encode-string user t))
      (smtpmail-command-or-throw process (base64-encode-string password t)))
     ((eq mech 'plain)
      ;; We used to send an empty initial request, and wait for an
      ;; empty response, and then send the password, but this
      ;; violate a SHOULD in RFC 2222 paragraph 5.1.  Note that this
      ;; is not sent if the server did not advertise AUTH PLAIN in
      ;; the EHLO response.  See RFC 2554 for more info.
      (smtpmail-command-or-throw
       process
       (concat "AUTH PLAIN "
               (base64-encode-string (concat "\0" user "\0" password) t))
       235))
     (t
      (error "Mechanism %s not implemented" mech)))))

(defun smtpmail-response-code (string)
  (when string
    (with-temp-buffer
      (insert string)
      (goto-char (point-min))
      (and (re-search-forward "^\\([0-9]+\\) " nil t)
           (string-to-number (match-string 1))))))

(defun smtpmail-ok-p (response &optional code)
  (and (car response)
       (integerp (car response))
       (< (car response) 400)
       (or (null code)
           (= code (car response)))))

(defun smtpmail-response-text (response)
  (mapconcat 'identity (cdr response) "\n"))

(defun smtpmail-query-smtp-server ()
  "Query for an SMTP server and try to contact it.
If the contact succeeds, customizes and saves `smtpmail-smtp-server'
and `smtpmail-smtp-service'.  This tries standard SMTP ports, and if
none works asks you to supply one.  If you know that you need to use
a non-standard port, you can set `smtpmail-smtp-service' in advance.
Returns an error if the server cannot be contacted."
  (let ((server (read-string "Outgoing SMTP mail server: "))
        (ports '(25 587))
        stream port prompted)
    (when (and smtpmail-smtp-service
               (not (member smtpmail-smtp-service ports)))
      (push smtpmail-smtp-service ports))
    (while (and (not smtpmail-smtp-server)
                (setq port (pop ports)))
      (if (not (setq stream (condition-case ()
                                (open-network-stream "smtp" nil server port)
                              (quit nil)
                              (error nil))))
          ;; We've used up the list of default ports, so query the user.
          (when (and (not ports)
                     (not prompted))
            (push (read-number (format "Port number to use when contacting %s? "
                                       server))
                  ports)
            (setq prompted t))
        (customize-save-variable 'smtpmail-smtp-server server)
        (customize-save-variable 'smtpmail-smtp-service port)
        (delete-process stream)))
    (unless smtpmail-smtp-server
      (error "Couldn't contact an SMTP server"))))

(defun smtpmail-user-mail-address ()
  "Return `user-mail-address' if it's a valid email address."
  (and user-mail-address
       (let ((parts (split-string user-mail-address "@")))
         (and (= (length parts) 2)
              ;; There's a dot in the domain name.
              (string-match "\\." (cadr parts))
              user-mail-address))))

(defun smtpmail-via-smtp (recipient smtpmail-text-buffer
                                    &optional ask-for-password)
  (unless smtpmail-smtp-server
    (smtpmail-query-smtp-server))
  (let ((process nil)
        (host (or smtpmail-smtp-server
                  (error "`smtpmail-smtp-server' not defined")))
        (port smtpmail-smtp-service)
        ;; `smtpmail-mail-address' should be set to the appropriate
        ;; buffer-local value by the caller, but in case not:
        (envelope-from
         (or smtpmail-mail-address
             (and mail-specify-envelope-from
                  (mail-envelope-from))
             (let ((from (mail-fetch-field "from")))
               (and from
                    (cadr (mail-extract-address-components from))))
             (smtpmail-user-mail-address)))
        response-code
        process-buffer
        result
        auth-mechanisms
        (supported-extensions '()))
    (unwind-protect
        (catch 'done
          ;; get or create the trace buffer
          (setq process-buffer
                (get-buffer-create
                 (format "*trace of SMTP session to %s*" host)))

          ;; clear the trace buffer of old output
          (with-current-buffer process-buffer
            (setq buffer-undo-list t)
            (erase-buffer))

          ;; open the connection to the server
          (let ((coding-system-for-read 'binary)
                (coding-system-for-write 'binary))
            (setq result
                  (open-network-stream
                   "smtpmail" process-buffer host port
                   :type smtpmail-stream-type
                   :return-list t
                   :warn-unless-encrypted ask-for-password
                   :capability-command (format "EHLO %s\r\n" (smtpmail-fqdn))
                   :end-of-command "^[0-9]+ .*\r\n"
                   :success "^2.*\n"
                   :always-query-capabilities t
                   :starttls-function
                   (lambda (capabilities)
                     (and (string-match "[ -]STARTTLS" capabilities)
                          "STARTTLS\r\n"))
                   :client-certificate t
                   :use-starttls-if-possible t)))

          ;; If we couldn't access the server at all, we give up.
          (unless (setq process (car result))
            (throw 'done (if (plist-get (cdr result) :error)
                             (plist-get (cdr result) :error)
                           "Unable to contact server")))

          ;; set the send-filter
          (set-process-filter process 'smtpmail-process-filter)

          (let* ((greeting (plist-get (cdr result) :greeting))
                 (code (smtpmail-response-code greeting)))
            (unless code
              (throw 'done (format "No greeting: %s" greeting)))
            (when (>= code 400)
              (throw 'done (format "Connection not allowed: %s" greeting))))

          (with-current-buffer process-buffer
            (set-buffer-process-coding-system 'raw-text-unix 'raw-text-unix)
            (make-local-variable 'smtpmail-read-point)
            (setq smtpmail-read-point (point-min))

            (let* ((capabilities (plist-get (cdr result) :capabilities))
                   (code (smtpmail-response-code capabilities)))
              (if (or (null code)
                      (>= code 400))
                  ;; The server didn't accept EHLO, so we fall back on HELO.
                  (smtpmail-command-or-throw
                   process (format "HELO %s" (smtpmail-fqdn)))
                ;; EHLO was successful, so we parse the extensions.
                (dolist (line (delete
                               ""
                               (split-string
                                (plist-get (cdr result) :capabilities)
                                "\r\n")))
                  (let ((name
                         (with-case-table ascii-case-table ;FIXME: Why?
                           (mapcar (lambda (s) (intern (downcase s)))
                                   (split-string (substring line 4) "[ ]")))))
                    (when (= (length name) 1)
                      (setq name (car name)))
                    (when name
                      (cond ((memq (if (consp name) (car name) name)
                                   '(verb xvrb 8bitmime onex xone
                                          expn size dsn etrn
                                          enhancedstatuscodes
                                          help xusr
                                          auth=login auth starttls))
                             (setq supported-extensions
                                   (cons name supported-extensions)))
                            (smtpmail-warn-about-unknown-extensions
                             (message "Unknown extension %s" name))))))))

            (setq auth-mechanisms
                  (smtpmail-try-auth-methods
                   process supported-extensions host port
                   ask-for-password))

            (when (or (member 'onex supported-extensions)
                      (member 'xone supported-extensions))
              (smtpmail-command-or-throw process (format "ONEX")))

            (when (and smtpmail-debug-verb
                       (or (member 'verb supported-extensions)
                           (member 'xvrb supported-extensions)))
              (smtpmail-command-or-throw process (format "VERB")))

            (when (member 'xusr supported-extensions)
              (smtpmail-command-or-throw process (format "XUSR")))

            ;; MAIL FROM:<sender>
            (let ((size-part
                   (if (or (member 'size supported-extensions)
                           (assoc 'size supported-extensions))
                       (format " SIZE=%d"
                               (with-current-buffer smtpmail-text-buffer
                                 ;; size estimate:
                                 (+ (- (point-max) (point-min))
                                    ;; Add one byte for each change-of-line
                                    ;; because of CR-LF representation:
                                    (count-lines (point-min) (point-max)))))
                     ""))
                  (body-part
                   (if (member '8bitmime supported-extensions)
                       ;; FIXME:
                       ;; Code should be added here that transforms
                       ;; the contents of the message buffer into
                       ;; something the receiving SMTP can handle.
                       ;; For a receiver that supports 8BITMIME, this
                       ;; may mean converting BINARY to BASE64, or
                       ;; adding Content-Transfer-Encoding and the
                       ;; other MIME headers.  The code should also
                       ;; return an indication of what encoding the
                       ;; message buffer is now, i.e. ASCII or
                       ;; 8BITMIME.
                       (if nil
                           " BODY=8BITMIME"
                         "")
                     "")))
              (smtpmail-send-command
               process (format "MAIL FROM:<%s>%s%s"
                               envelope-from size-part body-part))
              (cond
               ((smtpmail-ok-p (setq result (smtpmail-read-response process)))
                ;; Success.
                )
               ((and auth-mechanisms
                     (not ask-for-password)
                     (eq (car result) 530))
                ;; We got a "530 auth required", so we close and try
                ;; again, this time asking the user for a password.
                ;; We ignore any errors here, because some MTAs just
                ;; close the connection immediately after giving the
                ;; error message.
                (ignore-errors
                  (smtpmail-send-command process "QUIT")
                  (smtpmail-read-response process))
                (delete-process process)
                (setq process nil)
                (throw 'done
                       (smtpmail-via-smtp recipient smtpmail-text-buffer t)))
               (t
                ;; Return the error code.
                (throw 'done
                       (smtpmail-response-text result)))))

            ;; RCPT TO:<recipient>
            (let ((n 0))
              (while (not (null (nth n recipient)))
                (smtpmail-send-command
                 process (format "RCPT TO:<%s>"
                                 (smtpmail-maybe-append-domain
                                  (nth n recipient))))
                (cond
                 ((smtpmail-ok-p (setq result (smtpmail-read-response process)))
                  ;; Success.
                  nil)
                 ((and auth-mechanisms
                       (not ask-for-password)
                       (integerp (car result))
                       (>= (car result) 550)
                       (<= (car result) 554))
                  ;; We got a "550 relay not permitted" (or the like),
                  ;; and the server accepts credentials, so we try
                  ;; again, but ask for a password first.
                  (smtpmail-send-command process "QUIT")
                  (smtpmail-read-response process)
                  (delete-process process)
                  (setq process nil)
                  (throw 'done
                         (smtpmail-via-smtp recipient smtpmail-text-buffer t)))
                 (t
                  ;; Return the error code.
                  (throw 'done
                         (smtpmail-response-text result))))
                (setq n (1+ n))))

            ;; Send the contents.
            (smtpmail-command-or-throw process "DATA")
            (smtpmail-send-data process smtpmail-text-buffer)
            ;; DATA end "."
            (smtpmail-command-or-throw process ".")
            ;; Return success.
            nil))
      (when (and process
                 (buffer-live-p process-buffer))
        (with-current-buffer (process-buffer process)
          (smtpmail-send-command process "QUIT")
          (smtpmail-read-response process)
          (delete-process process)
          (unless smtpmail-debug-info
            (kill-buffer process-buffer)))))))


(defun smtpmail-process-filter (process output)
  (with-current-buffer (process-buffer process)
    (goto-char (point-max))
    (insert output)
    (set-marker (process-mark process) (point))))

(defun smtpmail-read-response (process)
  (let ((case-fold-search nil)
        (response-strings nil)
        (response-continue t)
        (return-value '(nil ()))
        match-end)
    (catch 'done
      (while response-continue
        (goto-char smtpmail-read-point)
        (while (not (search-forward "\r\n" nil t))
          (unless (memq (process-status process) '(open run))
            (throw 'done nil))
          (accept-process-output process)
          (goto-char smtpmail-read-point))

        (setq match-end (point))
        (setq response-strings
              (cons (buffer-substring smtpmail-read-point (- match-end 2))
                    response-strings))

        (goto-char smtpmail-read-point)
        (if (looking-at "[0-9]+ ")
            (let ((begin (match-beginning 0))
                  (end (match-end 0)))
              (if smtpmail-debug-info
                  (message "%s" (car response-strings)))

              (setq smtpmail-read-point match-end)

              ;; ignore lines that start with "0"
              (if (looking-at "0[0-9]+ ")
                  nil
                (setq response-continue nil)
                (setq return-value
                      (cons (string-to-number
                             (buffer-substring begin end))
                            (nreverse response-strings)))))

          (if (looking-at "[0-9]+-")
              (progn (if smtpmail-debug-info
                         (message "%s" (car response-strings)))
                     (setq smtpmail-read-point match-end)
                     (setq response-continue t))
            (progn
              (setq smtpmail-read-point match-end)
              (setq response-continue nil)
              (setq return-value
                    (cons nil (nreverse response-strings)))))))
      (setq smtpmail-read-point match-end))
    return-value))


(defun smtpmail-send-command (process command)
  (goto-char (point-max))
  (if (string-match "\\`AUTH [A-Z]+ " command)
      (insert (match-string 0 command) "<omitted>\r\n")
    (insert command "\r\n"))
  (setq smtpmail-read-point (point))
  (process-send-string process (concat command "\r\n")))

(defun smtpmail-send-data-1 (process data)
  (goto-char (point-max))

  (if (and (multibyte-string-p data)
           smtpmail-code-conv-from)
      (setq data (string-as-multibyte
                  (encode-coding-string data smtpmail-code-conv-from))))

  (if smtpmail-debug-info
      (insert data "\r\n"))

  (setq smtpmail-read-point (point))
  ;; Escape "." at start of a line
  (if (eq (string-to-char data) ?.)
      (process-send-string process "."))
  (process-send-string process data)
  (process-send-string process "\r\n"))

(defun smtpmail-send-data (process buffer)
  (let ((data-continue t) sending-data
        (pr (with-current-buffer buffer
              (make-progress-reporter "Sending email "
                                      (point-min) (point-max)))))
    (with-current-buffer buffer
      (goto-char (point-min)))
    (while data-continue
      (with-current-buffer buffer
        (progress-reporter-update pr (point))
        (setq sending-data (buffer-substring (point-at-bol) (point-at-eol)))
        (end-of-line 2)
        (setq data-continue (not (eobp))))
      (smtpmail-send-data-1 process sending-data))
    (progress-reporter-done pr)))

(defun smtpmail-deduce-address-list (smtpmail-text-buffer header-start header-end)
  "Get address list suitable for smtp RCPT TO: <address>."
  (unwind-protect
      (with-current-buffer smtpmail-address-buffer
        (erase-buffer)
        (let ((case-fold-search t)
              (simple-address-list "")
              this-line
              this-line-end
              addr-regexp)
          (insert-buffer-substring smtpmail-text-buffer header-start header-end)
          (goto-char (point-min))
          ;; RESENT-* fields should stop processing of regular fields.
          (save-excursion
            (setq addr-regexp
                  (if (re-search-forward "^Resent-\\(to\\|cc\\|bcc\\):"
                                         header-end t)
                      "^Resent-\\(to\\|cc\\|bcc\\):"
                    "^\\(To:\\|Cc:\\|Bcc:\\)")))

          (while (re-search-forward addr-regexp header-end t)
            (replace-match "")
            (setq this-line (match-beginning 0))
            (forward-line 1)
            ;; get any continuation lines
            (while (and (looking-at "^[ \t]+") (< (point) header-end))
              (forward-line 1))
            (setq this-line-end (point-marker))
            (setq simple-address-list
                  (concat simple-address-list " "
                          (mail-strip-quoted-names (buffer-substring this-line this-line-end)))))
          (erase-buffer)
          (insert " " simple-address-list "\n")
          (subst-char-in-region (point-min) (point-max) 10 ?  t) ; newline --> blank
          (subst-char-in-region (point-min) (point-max) ?, ?  t) ; comma   --> blank
          (subst-char-in-region (point-min) (point-max)  9 ?  t) ; tab     --> blank

          (goto-char (point-min))
          ;; tidiness in case hook is not robust when it looks at this
          (while (re-search-forward "[ \t]+" header-end t) (replace-match " "))

          (goto-char (point-min))
          (let (recipient-address-list)
            (while (re-search-forward " \\([^ ]+\\) " (point-max) t)
              (backward-char 1)
              (setq recipient-address-list (cons (buffer-substring (match-beginning 1) (match-end 1))
                                                 recipient-address-list)))
            (setq smtpmail-recipient-address-list recipient-address-list))))))

(defun smtpmail-do-bcc (header-end)
  "Delete [Resent-]BCC: and their continuation lines from the header area.
There may be multiple BCC: lines, and each may have arbitrarily
many continuation lines."
  (let ((case-fold-search t))
    (save-excursion
      (goto-char (point-min))
      ;; iterate over all BCC: lines
      (while (re-search-forward "^\\(RESENT-\\)?BCC:" header-end t)
        (delete-region (match-beginning 0)
                       (progn (forward-line 1) (point)))
        ;; get rid of any continuation lines
        (while (and (looking-at "^[ \t].*\n") (< (point) header-end))
          (replace-match ""))))))

(provide 'smtpmail)

;;; smtpmail.el ends here