Invoking an editor within mail

As you compose your message, be careful not to type a tilde ~ at the beginning of any line. This is a special escape character for controlling the behavior of mail. Here are some useful commands:
~p Prints the message as it is so far
~e Invokes an editor for editing the message.
The ~e feature requires some explanation. The message gets copied to a temporary file and the editor specified by your EDITOR shell environment variable is invoked on that file. You may continue composing or correcting your message within the editor. Then you must save the file (same name) and exit the editor to return to mail. At this point it is a good idea to type ~p to recheck the message before sending it with Ctrl-d.