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

.ip \fBedit\fP
To edit individual messages using the text editor, the
.b edit
command is provided.  The
.b edit
command takes a list of messages as described under the
.b type
command and processes each by writing it into the file
Message\c
.i x
where
.i x
is the message number being edited and executing the text editor on it.
When you have edited the message to your satisfaction, write the message
out and quit, upon which
.i Mail
will read the message back and remove the file.
.b Edit
may be abbreviated to
.b e .