This chapter describes the usual Emacs mode for editing and sending
mail---Mail mode. Emacs has alternative facilities for editing and
sending mail, including MH-E and Message mode, not documented in this
manual. You can choose any of them as your preferred method. The
commands C-x m, C-x 4 m and C-x 5 m use whichever
agent you have specified. So do various other Emacs commands and
facilities that send mail.
To specify your mail-composition method, set the variable
mail-user-agent. Currently legitimate values include
sendmail-user-agent, mh-e-user-agent, and
message-user-agent.
If you select a different mail-composition method, the information in
this chapter about the `*mail*' buffer and Mail mode does not
apply; other methods may use completely different commands with a
different format in a differently named buffer.