Walter Roberson <roberson@hamer.ibd.nrc.ca> writes:

  Under IRIX 5.2, set the environment variable MAILHOST to the name of
  the mail server, and set the zmail variable 'use_pop'.  You may also
  wish to set the zmail variable 'pop_options' to have mail retained on
  the server. Your userids on the machine with MediaMail and on the POP
  server must be the same.

  Under IRIX 5.3 all of the above still applies as well as the
  following: You can set the zmail variable 'mailhost' instead of the
  environment variable MAILHOST.  You can set the zmail variable
  'pop_user' to your userid on the POP server if it is different from
  your local userid.

  Note that MediaMail, like any POP client, cannot send mail to the POP
  server, only retrieve mail which has been sent to the server. That's
  just fine; doing the above doesn't prevent MediaMail from delivering
  mail normally.

  "Digital Media Execution Environment and Tools 5.5", at
  http://www.sgi.com/Products/Evaluation/dmedia/dmedia.html, includes an
  updated version of MediaMail for IRIX 5.3.