/bin/mail lock protocol

[John Stewart]

Does anyone know what style of locks /bin/mail uses when delivering mail
to a mail folder in /var/spool/mail?  Since the SunOS System and Network
Administration manual specifically talks about exporting /var/spool/mail
to client machines, I would expect that /bin/mail uses lockf style locks.

What puzzles me is that the Elm mailer seems to work ok on our server (the
machine on which /var/spool/mail actually resides) even though it uses
flock style locking.