> 
> Basically, it runs as a daemon and delivers local mail, but has a problem
> relaying mail. Since the machine is the backup MX for a number of domains,
> it gets a fair bit of email once in a while which ends up sitting in the
> queue. When I try to manually run the queue (sendmail -v -q), I see the
> first of many emails begin to be delivered, but then it segfaults. But I
> don't see a core.
> 
Are you sure that you don't get any core somewhere?  Doesn't sendmail
chroot to some non-obvious place? Is user mail allowed to write a core
file in its directory?  Can you turn on any debug flags?

Just a chance,

-- Ragge