EDIT  -  edit the current message

Usage: EDIT  

The EDIT command, in READ MODE, edits the message you have just read.
  The editor used is defined with SET EDITOR; the default is emacs.  
  The main purpose of editing received mail is to save only part of a 
  long message, or to fix a typo.

For more help, type "help" and one of these topics: 
    set editor   other   text-mode
