check

CHECK  -  check for new messages

Usage:  CHECK

The CHECK command checks for new mail in /usr/spool/mail.  If there is 
  any, MM will copy it into your mail file and display a header for 
  each new message.  Otherwise, the response is "No new mail.".

MM normally does not check for mail during SEND MODE, but will do so as
  soon as you return to TOP-LEVEL (MM> prompt).  CHECK lets you do an 
  additional check when you want to.

For more help, type "help" and one of the following:
  information   set check-interval   set continuous-check