To use Mail interactively, enter the following command at the DCL
    prompt:

    $ MAIL

    The Mail utility responds with the following prompt:

    MAIL>

    Once Mail is invoked, you can enter any of the Mail commands. To
    exit from Mail, enter the EXIT command at the MAIL> prompt.

    MAIL> EXIT

    You can also exit from Mail by pressing Ctrl/Z or entering the
    QUIT command.