I recently upgraded my server from 4.2 to 6.0, and since
then have been unable to get mail.  It turns out that slocal
(which I use to filter my mail) wasn't allowed to be run
from sendmail.  Finally figured out that a link to
/usr/lib/nmh/slocal is necessary in /etc/smrsh in order to
allow it to function.

IMHO this link should be standard, since slocal is a
*standard* mail handling program.  Since smrsh functionality
is a new thing since 4.2, it seems to me that existing
functionality (standard functionality at that) shouldn't be
broken.

%postinstall
ln -sf /usr/lib/nmh/slocal /etc/smrsh/slocal

%postuninstall
rm -f /etc/smrsh/slocal