[SunHELP] sendmail question

[Chance, Chad]

OK, I know this isn't sendmailhelp but I figured someone on this list might
be able to help me, plus it's running on a SS10 so it is sort of relevant...

Here's the situation: I am trying to host 4 different domain's mail with
this one box but I am having problems.
Just for simplicity, domain1.com, domain2.com, domain3.com, domain4.com.

The box is actually part of domain1, domain1's e-mail works sometimes, see
further explanation below.
domain2 is the first virtually hosted e-mail and it works great
domain3 worked for a week and now does not, see further explanation below
domain4 I am hosting for a friend and he hasn't got his domain records
updated evidently, so I'm not worried about that one at the moment

domain1 will sometimes bounce back with a host unknown error, I assume that
this is a DNS problem out on the internet somewhere and can't do anything
about it.

domain3's e-mail is hitting the box but is getting dumped into mqueue and is
sitting there with deferred status  (Mhost map: lookup (domain3.com):
deferred)
What bothers me about domain3 is that it is set up just like domain2 and
that it worked for a week and now doesn't, there have been no changes on the
box during that time.

It seems that the sendmail.org site is not as helpful as it used to be and
keeps referring me to the sendmail book which I can't afford right now.
It also seems, after a few searches with google, that quite a few other
people have had this same problem but, I have yet to find an explanation of
why this happens and how to fix it.

Config info:
SS10
OpenBSD 2.8 
sendmail 8.10.1

Any help or pointers would be appreciated, 
Chad