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 checks for mail during a session at frequent intervals.  
  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
  set incoming-mail   set append-new-mail
