There are two commands to send a message you have been editing:
If you want to send a message and be done with it, type C-c
mail-send-and-exit). This sends the message and then
either deletes the window or switches to another buffer. It also
“buries” the mail buffer, putting it at the lowest priority for
reselection. This is the usual command for sending a message.
The command C-c C-s (
message-send) sends the message
and marks the mail buffer unmodified, but leaves the buffer selected.
Use this command if you want to modify the message (perhaps with new
recipients) and send it again.
Sending a message runs the hook
In a file-visiting buffer, sending the message does not clear the modified flag, because only saving the file should do that. Also, you don't get a warning if you try to send the same message twice.
When you send a message containing non-ASCII characters,
they need to be encoded with a coding system (see Coding Systems).
Usually the coding system is specified automatically by your chosen
language environment (see Language Environments). You can
explicitly specify the coding system for outgoing mail by setting the
sendmail-coding-system (see Recognize Coding). 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.
send-mail-function controls how the default mail
user agent sends mail. Its value should be a function, which can be
one of the following:
smtpmail-auth-credentials. See .
sendmail-send-it, but allows you to queue messages for later sending. See the commentary section in the file feedmail.el for more information.