Ultrix mail fun

[Bob DeBula]

We are running Ultrix 4.1 on two DEC 5500s and had decided to
do a little work to secure /usr/spool/mail.  We changed 
permissions on the /usr/var/spool/mail directory to drwxrwxr-x 
(775).  We knew that we would have to touch a file in 
/usr/var/spool/mail for each user and change ownership and
to their ID with read & write permissions (and we did that).
We were loosely modeling what we're doing on the setup 
on our HP-UX 7.0 system.  We changed ELM so that it had
setgid for "mail".  Everything seems to work well *except*
/usr/bin/mail (which has setuid "root" and setgid "kmem").
First question: why setgid "kmem" (suspect it's a leftover
from when "mail" may have had the same UNIX id number)?
      
/usr/bin/mail seems to hang forever when invoked in this
new configuration.  We decided to try changing the group
on /usr/bin/mail to "mail". This apparently allows it
to continue on, but now it doesn't recognize any mail which is
queued (i.e. it just terminates immediately).

It would appear that for some weird reason, /usr/bin/mail
is checking directory permissions on /usr/var/spool/mail
and terminating immediately if it doesn't like what it sees.

Any ideas on why this is so?

/usr/ucb/mail works fine, incidently.

The reason for doing this in the first place was to keep quota
restricted users from using /usr/var/spool/mail as a storage area.

Thanks in advance for any help/enlightenment you may be able to offer.