read-mail-command

read-mail-command is a variable defined in `simple.el'.
Its value is

rmail

• This variable may be risky if used as a file-local variable.

Documentation:
Your preference for a mail reading package.
This is used by some keybindings which support reading mail.
See also `mail-user-agent' concerning sending mail.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 21.1 of Emacs.