Variable: mail-send-hook
mail-send-hook is a customizable variable defined in sendmail.el.gz.
Value
nil
Documentation
Hook run just before sending a message.
Probably introduced at or before Emacs version 19.23.
Source Code
;; Defined in /usr/src/emacs/lisp/mail/sendmail.el.gz
(defcustom mail-send-hook nil
"Hook run just before sending a message."
:type 'hook
:options '(flyspell-mode-off))