V8/usr/src/cmd/Mail/manual/cmds/mail

.ip \fBmail\fP
Send mail to one or more people.  If you have the
.i ask
option set,
.i Mail
will prompt you for a subject to your message.  Then you
can type in your message, using tilde escapes as described in
section 4 to edit, print, or modify your message.  To signal your
satisfaction with the message and send it, type control-d at the
beginning of a line, or a . alone on a line if you set the option
.i dot .
To abort the message, type two interrupt characters (\s-2RUBOUT\s0
by default) in a row or use the
.b ~q
escape.