set movemail-path

SET MOVEMAIL-PATH filename  -  locate the movemail program
Usually:          /usr/local/lib/mm/movemail

The MOVEMAIL-PATH variable defines the path to the movemail program, used 
  by MM to move mail from the spool directory to your home directory, from
  which MM can move it to the MAIL-FILE.  Do not change this.

For more help, type "help" and one of the following:
(at any prompt:)  save-init   set   show   check   set incoming-mail
                  set mail-file