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+@c This is part of the Emacs manual.
+@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc.
+@c See file emacs.texi for copying conditions.
+@node Sending Mail, Rmail, Picture, Top
+@chapter Sending Mail
+@cindex sending mail
+@cindex mail
+@cindex message
+
+  To send a message in Emacs, you start by typing a command (@kbd{C-x m})
+to select and initialize the @samp{*mail*} buffer.  Then you edit the text
+and headers of the message in this buffer, and type another command
+(@kbd{C-c C-s} or @kbd{C-c C-c}) to send the message.
+
+@table @kbd
+@item C-x m
+Begin composing a message to send (@code{compose-mail}).
+@item C-x 4 m
+Likewise, but display the message in another window
+(@code{compose-mail-other-window}).
+@item C-x 5 m
+Likewise, but make a new frame (@code{compose-mail-other-frame}).
+@item C-c C-s
+In Mail mode, send the message (@code{mail-send}).
+@item C-c C-c
+Send the message and bury the mail buffer (@code{mail-send-and-exit}).
+@end table
+
+@kindex C-x m
+@findex compose-mail
+@kindex C-x 4 m
+@findex compose-mail-other-window
+@kindex C-x 5 m
+@findex compose-mail-other-frame
+  The command @kbd{C-x m} (@code{compose-mail}) selects a buffer named
+@samp{*mail*} and initializes it with the skeleton of an outgoing
+message.  @kbd{C-x 4 m} (@code{compose-mail-other-window}) selects the
+@samp{*mail*} buffer in a different window, leaving the previous current
+buffer visible.  @kbd{C-x 5 m} (@code{compose-mail-other-frame}) creates
+a new frame to select the @samp{*mail*} buffer.
+
+  Because the mail-composition buffer is an ordinary Emacs buffer, you can
+switch to other buffers while in the middle of composing mail, and switch
+back later (or never).  If you use the @kbd{C-x m} command again when you
+have been composing another message but have not sent it, you are asked to
+confirm before the old message is erased.  If you answer @kbd{n}, the
+@samp{*mail*} buffer is left selected with its old contents, so you can
+finish the old message and send it.  @kbd{C-u C-x m} is another way to do
+this.  Sending the message marks the @samp{*mail*} buffer ``unmodified,''
+which avoids the need for confirmation when @kbd{C-x m} is next used.
+
+  If you are composing a message in the @samp{*mail*} buffer and want to
+send another message before finishing the first, rename the
+@samp{*mail*} buffer using @kbd{M-x rename-uniquely} (@pxref{Misc
+Buffer}).  Then you can use @kbd{C-x m} or its variants described above
+to make a new @samp{*mail*} buffer.  Once you've done that, you can work
+with each mail buffer independently.
+
+@menu
+* Format: Mail Format.	     Format of the mail being composed.
+* Headers: Mail Headers.     Details of permitted mail header fields.
+* Aliases: Mail Aliases.     Abbreviating and grouping mail addresses.
+* Mode: Mail Mode.	     Special commands for editing mail being composed.
+* Spook: Distracting NSA.    How to distract the NSA's attention.
+* Mail Methods::             Using alternative mail-composition methods.
+@end menu
+
+@node Mail Format
+@section The Format of the Mail Buffer
+
+  In addition to the @dfn{text} or @dfn{body}, a message has @dfn{header
+fields} which say who sent it, when, to whom, why, and so on.  Some
+header fields, such as @samp{Date} and @samp{Sender}, are created
+automatically when you send the message.  Others, such as the recipient
+names, must be specified by you in order to send the message properly.
+
+  Mail mode provides a few commands to help you edit some header fields,
+and some are preinitialized in the buffer automatically at times.  You can
+insert and edit header fields using ordinary editing commands.
+
+  The line in the buffer that says
+
+@example
+--text follows this line--
+@end example
+
+@noindent
+is a special delimiter that separates the headers you have specified from
+the text.  Whatever follows this line is the text of the message; the
+headers precede it.  The delimiter line itself does not appear in the
+message actually sent.  The text used for the delimiter line is controlled
+by the variable @code{mail-header-separator}.
+
+Here is an example of what the headers and text in the mail buffer
+might look like.
+
+@example
+To: gnu@@gnu.org
+CC: lungfish@@spam.org, byob@@spam.org
+Subject: The Emacs Manual
+--Text follows this line--
+Please ignore this message.
+@end example
+
+@node Mail Headers
+@section Mail Header Fields
+@cindex headers (of mail message)
+
+  A header field in the mail buffer starts with a field name at the
+beginning of a line, terminated by a colon.  Upper and lower case are
+equivalent in field names (and in mailing addresses also).  After the
+colon and optional whitespace comes the contents of the field.
+
+  You can use any name you like for a header field, but normally people
+use only standard field names with accepted meanings.  Here is a table
+of fields commonly used in outgoing messages.
+
+@table @samp
+@item To
+This field contains the mailing addresses to which the message is
+addressed.  If you list more than one address, use commas, not spaces,
+to separate them.
+
+@item Subject
+The contents of the @samp{Subject} field should be a piece of text
+that says what the message is about.  The reason @samp{Subject} fields
+are useful is that most mail-reading programs can provide a summary of
+messages, listing the subject of each message but not its text.
+
+@item CC
+This field contains additional mailing addresses to send the message to,
+like @samp{To} except that these readers should not regard the message
+as directed at them.
+
+@item BCC
+This field contains additional mailing addresses to send the message to,
+which should not appear in the header of the message actually sent.
+Copies sent this way are called @dfn{blind carbon copies}.
+
+@vindex mail-self-blind
+To send a blind carbon copy of every outgoing message to yourself, set
+the variable @code{mail-self-blind} to @code{t}.
+
+@item FCC
+This field contains the name of one file and directs Emacs to append a
+copy of the message to that file when you send the message.  If the file
+is in Rmail format, Emacs writes the message in Rmail format; otherwise,
+Emacs writes the message in system mail file format.
+
+@vindex mail-archive-file-name
+To put a fixed file name in the @samp{FCC} field each time you start
+editing an outgoing message, set the variable
+@code{mail-archive-file-name} to that file name.  Unless you remove the
+@samp{FCC} field before sending, the message will be written into that
+file when it is sent.
+
+@item From
+Use the @samp{From} field to say who you are, when the account you are
+using to send the mail is not your own.  The contents of the @samp{From}
+field should be a valid mailing address, since replies will normally go
+there.  If you don't specify the @samp{From} field yourself, Emacs uses
+the value of @code{user-mail-address} as the default.
+
+@item Reply-to
+Use this field to direct replies to a different address.  Most
+mail-reading programs (including Rmail) automatically send replies to
+the @samp{Reply-to} address in preference to the @samp{From} address.
+By adding a @samp{Reply-to} field to your header, you can work around
+any problems your @samp{From} address may cause for replies.
+
+@cindex @code{REPLYTO} environment variable
+@vindex mail-default-reply-to
+To put a fixed @samp{Reply-to} address into every outgoing message, set
+the variable @code{mail-default-reply-to} to that address (as a string).
+Then @code{mail} initializes the message with a @samp{Reply-to} field as
+specified.  You can delete or alter that header field before you send
+the message, if you wish.  When Emacs starts up, if the environment
+variable @code{REPLYTO} is set, @code{mail-default-reply-to} is
+initialized from that environment variable.
+
+@item In-reply-to
+This field contains a piece of text describing a message you are
+replying to.  Some mail systems can use this information to correlate
+related pieces of mail.  Normally this field is filled in by Rmail
+when you reply to a message in Rmail, and you never need to
+think about it (@pxref{Rmail}).
+
+@item References
+This field lists the message IDs of related previous messages.  Rmail
+sets up this field automatically when you reply to a message.
+@end table
+
+  The @samp{To}, @samp{CC}, @samp{BCC} and @samp{FCC} header fields can
+appear any number of times, and each such header field can contain
+multiple addresses, separated by commas.  This way, you can specify any
+number of places to send the message.  A @samp{To}, @samp{CC}, or
+@samp{BCC} field can also have continuation lines: one or more lines
+starting with whitespace, following the starting line of the field, are
+considered part of the field.  Here's an example of a @samp{To} field
+with a continuation line:@refill
+
+@example
+@group
+To: foo@@here.net, this@@there.net,
+  me@@gnu.cambridge.mass.usa.earth.spiral3281
+@end group
+@end example
+
+@vindex mail-from-style
+  When you send the message, if you didn't write a @samp{From} field
+yourself, Emacs puts in one for you.  The variable
+@code{mail-from-style} controls the format:
+
+@table @code
+@item nil
+Use just the email address, as in @samp{king@@grassland.com}.
+@item parens
+Use both email address and full name, as in @samp{king@@grassland.com (Elvis
+Parsley)}.
+@item angles
+Use both email address and full name, as in @samp{Elvis Parsley
+<king@@grassland.com>}.
+@item system-default
+Allow the system to insert the @samp{From} field.
+@end table
+
+@node Mail Aliases
+@section Mail Aliases
+@cindex mail aliases
+@cindex @file{.mailrc} file
+@cindex mailrc file
+
+  You can define @dfn{mail aliases} in a file named @file{~/.mailrc}.
+These are short mnemonic names which stand for mail addresses or groups of
+mail addresses.  Like many other mail programs, Emacs expands aliases
+when they occur in the @samp{To}, @samp{From}, @samp{CC}, @samp{BCC}, and
+@samp{Reply-to} fields, plus their @samp{Resent-} variants.
+
+  To define an alias in @file{~/.mailrc}, write a line in the following
+format:
+
+@example
+alias @var{shortaddress} @var{fulladdresses}
+@end example
+
+@noindent
+Here @var{fulladdresses} stands for one or more mail addresses for
+@var{shortaddress} to expand into.  Separate multiple addresses with
+spaces; if an address contains a space, quote the whole address with a
+pair of double-quotes.
+
+For instance, to make @code{maingnu} stand for
+@code{gnu@@gnu.org} plus a local address of your own, put in
+this line:@refill
+
+@example
+alias maingnu gnu@@gnu.org local-gnu
+@end example
+
+  Emacs also recognizes include commands in @samp{.mailrc} files.
+They look like this:
+
+@example
+source @var{filename}
+@end example
+
+@noindent
+The file @file{~/.mailrc} is used primarily by other mail-reading
+programs; it can contain various other commands.  Emacs ignores
+everything in it except for alias definitions and include commands.
+
+@findex define-mail-alias
+  Another way to define a mail alias, within Emacs alone, is with the
+@code{define-mail-alias} command.  It prompts for the alias and then the
+full address.  You can use it to define aliases in your @file{.emacs}
+file, like this:
+
+@example
+(define-mail-alias "maingnu" "gnu@@gnu.org")
+@end example
+
+@vindex mail-aliases
+  @code{define-mail-alias} records aliases by adding them to a
+variable named @code{mail-aliases}.  If you are comfortable with
+manipulating Lisp lists, you can set @code{mail-aliases} directly.  The
+initial value of @code{mail-aliases} is @code{t}, which means that
+Emacs should read @file{.mailrc} to get the proper value.
+
+@vindex mail-personal-alias-file
+  You can specify a different file name to use instead of
+@file{~/.mailrc} by setting the variable
+@code{mail-personal-alias-file}.
+
+@findex expand-mail-aliases
+  Normally, Emacs expands aliases when you send the message.  You do not
+need to expand mail aliases before sending the message, but you can
+expand them if you want to see where the mail will actually go.  To do
+this, use the command @kbd{M-x expand-mail-aliases}; it expands all mail
+aliases currently present in the mail headers that hold addresses.
+
+  If you like, you can have mail aliases expand as abbrevs, as soon as
+you type them in (@pxref{Abbrevs}).  To enable this feature, execute the
+following:
+
+@example
+(add-hook 'mail-setup-hook 'mail-abbrevs-setup)
+@end example
+
+@noindent
+@findex define-mail-abbrev
+@vindex mail-abbrevs
+This can go in your @file{.emacs} file.  @xref{Hooks}.  If you use this
+feature, you must use @code{define-mail-abbrev} instead of
+@code{define-mail-alias}; the latter does not work with this package.
+Note that the mail abbreviation package uses the variable
+@code{mail-abbrevs} instead of @code{mail-aliases}, and that all alias
+names are converted to lower case.
+
+@kindex C-c C-a @r{(Mail mode)}
+@findex mail-interactive-insert-alias
+  The mail abbreviation package also provides the @kbd{C-c C-a}
+(@code{mail-interactive-insert-alias}) command, which reads an alias
+name (with completion) and inserts its definition at point.  This is
+useful when editing the message text itself or a header field such as
+@samp{Subject} in which Emacs does not normally expand aliases.
+
+  Note that abbrevs expand only if you insert a word-separator character
+afterward.  However, you can rebind @kbd{C-n} and @kbd{M->} to cause
+expansion as well.  Here's how to do that:
+
+@smallexample
+(add-hook 'mail-setup-hook
+          '(lambda ()
+             (substitute-key-definition
+               'next-line 'mail-abbrev-next-line
+               mail-mode-map global-map)
+             (substitute-key-definition
+               'end-of-buffer 'mail-abbrev-end-of-buffer
+               mail-mode-map global-map)))
+@end smallexample
+
+@node Mail Mode
+@section Mail Mode
+@cindex Mail mode
+@cindex mode, Mail
+
+  The major mode used in the mail buffer is Mail mode, which is much
+like Text mode except that various special commands are provided on the
+@kbd{C-c} prefix.  These commands all have to do specifically with
+editing or sending the message.  In addition, Mail mode defines the
+character @samp{%} as a word separator; this is helpful for using the
+word commands to edit mail addresses.
+
+  Mail mode is normally used in buffers set up automatically by the
+@code{mail} command and related commands.  However, you can also switch
+to Mail mode in a file-visiting buffer.  That is a useful thing to do if
+you have saved draft message text in a file.
+
+@menu
+* Mail Sending::        Commands to send the message.
+* Header Editing::      Commands to move to header fields and edit them.
+* Citing Mail::         Copying all or part of a message you are replying to.
+* Mail Mode Misc::      Spell checking, signatures, etc.
+@end menu
+
+@node Mail Sending
+@subsection Mail Sending
+
+  Mail mode has two commands for sending the message you have been
+editing:
+
+@table @kbd
+@item C-c C-s
+Send the message, and leave the mail buffer selected (@code{mail-send}).
+@item C-c C-c
+Send the message, and select some other buffer (@code{mail-send-and-exit}).
+@end table
+
+@kindex C-c C-s @r{(Mail mode)}
+@kindex C-c C-c @r{(Mail mode)}
+@findex mail-send
+@findex mail-send-and-exit
+  @kbd{C-c C-s} (@code{mail-send}) sends the message and marks the mail
+buffer unmodified, but leaves that buffer selected so that you can
+modify the message (perhaps with new recipients) and send it again.
+@kbd{C-c C-c} (@code{mail-send-and-exit}) sends and then deletes the
+window or switches to another buffer.  It puts the mail buffer at the
+lowest priority for reselection by default, since you are finished with
+using it.  This is the usual way to send the message.
+
+  In a file-visiting buffer, sending the message does not clear the
+modified flag, because only saving the file should do that.  As a
+result, you don't get a warning if you try to send the same message
+twice.
+
+@vindex sendmail-coding-system
+  When you send a message that contains non-ASCII characters, they need
+to be encoded with a coding system (@pxref{Coding Systems}).  Usually
+the coding system is specified automatically by your chosen language
+environment (@pxref{Language Environments}).  You can explicitly specify
+the coding system for outgoing mail by setting the variable
+@code{sendmail-coding-system}.
+
+  If the coding system thus determined does not handle the characters in
+a particular message, Emacs asks you to select the coding system to use,
+showing a list of possible coding systems.
+
+@node Header Editing
+@subsection Mail Header Editing
+
+  Mail mode provides special commands to move to particular header
+fields and to complete addresses in headers.
+
+@table @kbd
+@item C-c C-f C-t
+Move to the @samp{To} header field, creating one if there is none
+(@code{mail-to}).
+@item C-c C-f C-s
+Move to the @samp{Subject} header field, creating one if there is
+none (@code{mail-subject}).
+@item C-c C-f C-c
+Move to the @samp{CC} header field, creating one if there is none
+(@code{mail-cc}).
+@item C-c C-f C-b
+Move to the @samp{BCC} header field, creating one if there is none
+(@code{mail-bcc}).
+@item C-c C-f C-f
+Move to the @samp{FCC} header field, creating one if there is none
+(@code{mail-fcc}).
+@item M-@key{TAB}
+Complete a mailing address (@code{mail-complete}).
+@end table
+
+@kindex C-c C-f C-t @r{(Mail mode)}
+@findex mail-to
+@kindex C-c C-f C-s @r{(Mail mode)}
+@findex mail-subject
+@kindex C-c C-f C-c @r{(Mail mode)}
+@findex mail-cc
+@kindex C-c C-f C-b @r{(Mail mode)}
+@findex mail-bcc
+@kindex C-c C-f C-f @r{(Mail mode)}
+@findex mail-fcc
+  There are five commands to move point to particular header fields, all
+based on the prefix @kbd{C-c C-f} (@samp{C-f} is for ``field'').  They
+are listed in the table above.  If the field in question does not exist,
+these commands create one.  We provide special motion commands for these
+particular fields because they are the fields users most often want to
+edit.
+
+@findex mail-complete
+@kindex M-TAB @r{(Mail mode)}
+  While editing a header field that contains mailing addresses, such as
+@samp{To:}, @samp{CC:} and @samp{BCC:}, you can complete a mailing
+address by typing @kbd{M-@key{TAB}} (@code{mail-complete}).  It inserts
+the full name corresponding to the address, if it can determine the full
+name.  The variable @code{mail-complete-style} controls whether to insert
+the full name, and what style to use, as in @code{mail-from-style}
+(@pxref{Mail Headers}).
+
+  For completion purposes, the valid mailing addresses are taken to be
+the local users' names plus your personal mail aliases.  You can specify
+additional sources of valid addresses; use the customization buffer
+to see the options for this.
+
+  If you type @kbd{M-@key{TAB}} in the body of the message, it invokes
+@code{ispell-complete-word}, as in Text mode.
+
+@node Citing Mail
+@subsection Citing Mail
+@cindex citing mail
+
+  Mail mode also has commands for yanking or @dfn{citing} all or part of
+a message that you are replying to.  These commands are active only when
+you started sending a message using an Rmail command.
+
+@table @kbd
+@item C-c C-y
+Yank the selected message from Rmail (@code{mail-yank-original}).
+@item C-c C-r
+Yank the region from the Rmail buffer (@code{mail-yank-region}).
+@item C-c C-q
+Fill each paragraph cited from another message
+(@code{mail-fill-yanked-message}).
+@end table
+
+@kindex C-c C-y @r{(Mail mode)}
+@findex mail-yank-original
+  When mail sending is invoked from the Rmail mail reader using an Rmail
+command, @kbd{C-c C-y} can be used inside the mail buffer to insert
+the text of the message you are replying to.  Normally it indents each line
+of that message three spaces and eliminates most header fields.  A numeric
+argument specifies the number of spaces to indent.  An argument of just
+@kbd{C-u} says not to indent at all and not to eliminate anything.
+@kbd{C-c C-y} always uses the current message from the Rmail buffer,
+so you can insert several old messages by selecting one in Rmail,
+switching to @samp{*mail*} and yanking it, then switching back to
+Rmail to select another.
+
+@vindex mail-yank-prefix
+  You can specify the text for @kbd{C-c C-y} to insert at the beginning
+of each line: set @code{mail-yank-prefix} to the desired string.  (A
+value of @code{nil} means to use indentation; this is the default.)
+However, @kbd{C-u C-c C-y} never adds anything at the beginning of the
+inserted lines, regardless of the value of @code{mail-yank-prefix}.
+
+@kindex C-c C-r @r{(Mail mode)}
+@findex mail-yank-region
+  To yank just a part of an incoming message, set the region in Rmail to
+the part you want; then go to the @samp{*Mail*} message and type
+@kbd{C-c C-r} (@code{mail-yank-region}).  Each line that is copied is
+indented or prefixed according to @code{mail-yank-prefix}.
+
+@kindex C-c C-q @r{(Mail mode)}
+@findex mail-fill-yanked-message
+  After using @kbd{C-c C-y} or @kbd{C-c C-r}, you can type @kbd{C-c C-q}
+(@code{mail-fill-yanked-message}) to fill the paragraphs of the yanked
+old message or messages.  One use of @kbd{C-c C-q} fills all such
+paragraphs, each one individually.  To fill a single paragraph of the
+quoted message, use @kbd{M-q}.  If filling does not automatically
+handle the type of citation prefix you use, try setting the fill prefix
+explicitly.  @xref{Filling}.
+
+@node Mail Mode Misc
+@subsection Mail Mode Miscellany
+
+@table @kbd
+@item C-c C-t
+Move to the beginning of the message body text (@code{mail-text}).
+@item C-c C-w
+Insert the file @file{~/.signature} at the end of the message text
+(@code{mail-signature}).
+@item C-c C-i @var{file} @key{RET}
+Insert the contents of @var{file} at the end of the outgoing message
+(@code{mail-attach-file}).
+@item M-x ispell-message
+Do spelling correction on the message text, but not on citations from
+other messages.
+@end table
+
+@kindex C-c C-t @r{(Mail mode)}
+@findex mail-text
+  @kbd{C-c C-t} (@code{mail-text}) moves point to just after the header
+separator line---that is, to the beginning of the message body text.
+
+@kindex C-c C-w @r{(Mail mode)}
+@findex mail-signature
+@vindex mail-signature
+  @kbd{C-c C-w} (@code{mail-signature}) adds a standard piece of text at
+the end of the message to say more about who you are.  The text comes
+from the file @file{~/.signature} in your home directory.  To insert
+your signature automatically, set the variable @code{mail-signature} to
+@code{t}; then starting a mail message automatically inserts the
+contents of your @file{~/.signature} file.  If you want to omit your
+signature from a particular message, delete it from the buffer before
+you send the message.
+
+  You can also set @code{mail-signature} to a string; then that string
+is inserted automatically as your signature when you start editing a
+message to send.  If you set it to some other Lisp expression, the
+expression is evaluated each time, and its value (which should be a
+string) specifies the signature.
+
+@findex ispell-message
+  You can do spelling correction on the message text you have written
+with the command @kbd{M-x ispell-message}.  If you have yanked an
+incoming message into the outgoing draft, this command skips what was
+yanked, but it checks the text that you yourself inserted.  (It looks
+for indentation or @code{mail-yank-prefix} to distinguish the cited
+lines from your input.)  @xref{Spelling}.
+
+@kindex C-c C-i @r{(Mail mode)}
+@findex mail-attach-file
+  To include a file in the outgoing message, you can use @kbd{C-x i},
+the usual command to insert a file in the current buffer.  But it is
+often more convenient to use a special command, @kbd{C-c C-i}
+(@code{mail-attach-file}).  This command inserts the file contents at
+the end of the buffer, after your signature if any, with a delimiter
+line that includes the file name.
+
+@vindex mail-mode-hook
+@vindex mail-setup-hook
+  Turning on Mail mode (which @kbd{C-x m} does automatically) runs the
+normal hooks @code{text-mode-hook} and @code{mail-mode-hook}.
+Initializing a new outgoing message runs the normal hook
+@code{mail-setup-hook}; if you want to add special fields to your mail
+header or make other changes to the appearance of the mail buffer, use
+that hook.  @xref{Hooks}.
+
+  The main difference between these hooks is just when they are
+invoked.  Whenever you type @kbd{M-x mail}, @code{mail-mode-hook} runs
+as soon as the @samp{*mail*} buffer is created.  Then the
+@code{mail-setup} function puts in the default contents of the buffer.
+After these default contents are inserted, @code{mail-setup-hook} runs.
+
+@node Distracting NSA
+@section Distracting the NSA
+
+@findex spook
+@cindex NSA
+  @kbd{M-x spook} adds a line of randomly chosen keywords to an outgoing
+mail message.  The keywords are chosen from a list of words that suggest
+you are discussing something subversive.
+
+  The idea behind this feature is the suspicion that the NSA snoops on
+all electronic mail messages that contain keywords suggesting they might
+find them interesting.  (The NSA says they don't, but that's what they
+@emph{would} say.)  The idea is that if lots of people add suspicious
+words to their messages, the NSA will get so busy with spurious input
+that they will have to give up reading it all.
+
+  Here's how to insert spook keywords automatically whenever you start
+entering an outgoing message:
+
+@example
+(add-hook 'mail-setup-hook 'spook)
+@end example
+
+  Whether or not this confuses the NSA, it at least amuses people.
+
+@node Mail Methods
+@section Mail-Composition Methods
+@cindex mail-composition methods
+
+  This chapter describes the usual Emacs mode for editing and sending
+mail---Mail mode.  Emacs has alternative facilities for editing and
+sending mail, including MH-E and Message mode, not documented in this
+manual.  You can choose any of them as your preferred method.  The
+commands @code{C-x m}, @code{C-x 4 m} and @code{C-x 5 m} use whichever
+agent you have specified.  So do various other Emacs commands and
+facilities that send mail.
+
+@vindex mail-user-agent
+  To specify your mail-composition method, set the variable
+@code{mail-user-agent}.  Currently legitimate values include
+@code{sendmail-user-agent}, @code{mh-e-user-agent}, and
+@code{message-user-agent}.
+
+  If you select a different mail-composition method, the information in
+this chapter about the @samp{*mail*} buffer and Mail mode does not
+apply; other methods may use completely different commands with a
+different format in a differently named buffer.
+