I am having trouble with files getting stuck in
/var/spool/clientqueue.  Occassionally, the mailer fails for some
reason and leaves queued files there.  However, later they never seem
to be processed, even though subsequent mail gets sent fine.  I have
both sendmail and smmsp set to YES in /etc/rc.conf; otherwise, I am
using the default flags for both and the shipped version of
/etc/mail/submit.cf.

I suspect this is misconfigured in some way, but I'm not sure how.
Any guidance on how to fix this is welcome.  Thanks for your help.

Cheers,
Brook