quit

QUIT  -  leave MM; suspend the process 

Usage:  QUIT

The QUIT command  rewrites the current mail file if it was modified, 
  suspends the MM process,  and returns you to the shell.  Unlike the EXIT 
  command, it does not expunge deleted messages.  You can continue the MM
  process by typing mm to the shell.

The variable SUSPEND-ON-QUIT controls whether QUIT suspends MM.

There are three ways to leave MM.  The defaults are:
  EXIT	suspends MM	expunges deleted messages
  QUIT	suspends MM	does not expunge
  BYE	kills MM	asks whether to expunge

The command SUSPEND is very similar to QUIT.  SUSPEND always suspends,
  but does not rewrite the mail file if there were only minor changes.

For more help type "help" and one of these topics:
  exit   bye   suspend   z   basic   set suspend-on-quit