Compose a message with the MH mail system.
This function does not prompt the user for any header fields, and
thus is suitable for use by programs that want to create a mail
buffer. Users should use M-x mh-smail to compose mail.
Optional arguments for setting certain fields include TO,
SUBJECT, and OTHER-HEADERS. Additional arguments are IGNORED.
This function remains for Emacs 21 compatibility. New
applications should use `mh-user-agent-compose'.
(fn &optional TO SUBJECT OTHER-HEADERS &rest IGNORED)