message-send
message-send is an interactive compiled Lisp function in `message.el
'.
(message-send &optional ARG)
Send the message in the current buffer.
If `message-interactive' is non-nil, wait for success indication or
error messages, and inform user.
Otherwise any failure is reported in a message back to the user from
the mailer.
The usage of ARG is defined by the instance that called Message.
It should typically alter the sending method in some way or other.