Z (same as SUSPEND)  -  suspend MM

Usage:  Z 
   or:  control-z

The Z or SUSPEND command leaves MM and suspends the process.  This is almost 
  the same as QUIT, if the variable SUSPEND-ON-QUIT is yes; however, Z
  does not rewrite the mail file first, if there were only minor changes.

Continue the process later by typing either "fg", if MM was the last process
  you suspended (with Z or QUIT), or "mm", which, in our standard
  environment, means "fg -s /usr/local/bin/mm" (see /etc/kshenv1).

Example:
  MM>z          				#or "quit"
  [1] + Stopped (signal)  /usr/local/bin/mm
  $ fg                                          #or "mm"
  /usr/local/bin/mm
  MM>

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