NFS mounted /usr/spool/mail under SunOS 4.1

[Anthony A. Datri]

I've been trying to determine just what the locking issues are with NFS
mounting /usr/spool/mail.  Binmail is generally used by the server's
sendmail to do local delivery.  The binmail sources I have (sendmail 5.61)
don't do flock/fcntl on the mailbox -- does Sun's binmail do this locking?
Certain people here who are against the idea of NFS mounting
/usr/spool/mail (and doing mail on the workstations in general) say that
the world will blow up because of the non-locking (most of our mail
servers wouldn't be Suns).  Can anyone enlighten me on these issues?