message-smtpmail-send-it
message-smtpmail-send-it is a compiled Lisp function in `message.el
'.
(message-smtpmail-send-it)
Send the prepared message buffer with `smtpmail-send-it'.
The only difference from `smtpmail-send-it' is that this command
evaluates `message-send-mail-hook' just before sending a message.
It is useful if your ISP requires the POP-before-SMTP
authentication. See the Gnus manual for details.