Subject:   -53- Why can't I receive mail on an NFS-mounted mail spool
                under IRIX 5.2?
Date: 29 Aug 1994 00:00:01 EST

  IRIX 5.2 NFS has a bug which prevents writing to a zero-length file if
  the writing process has group write permission but not group read (or
  user write) permission. IRIX 5.2 /bin/mail likes to set the
  permissions of /var/mail/<user> to mode 620, exactly what is needed to
  exercise the NFS bug. There is no patch for these bugs, but both are
  fixed in IRIX 5.3. Meanwhile, you can work around the problem by
  chmod'ing your mail files to 660 and setting the appropriate option in
  your mail program to make sure that empty mail files are not removed.