Warning: newbie admin question incoming.

I am running Mailman 2.1 and Sendmail with RedHat 8.0. I have my sendmail simply configured to refuse relay for anything but local host deliveries.
i.e., people logged into Squirrel Mail can send, but I have no SMTP auth or SMTP after POP set or anything like that.

So, it seems that Mailman will reject any post to any list to the moderator for approval, even with all the proper moderation tags set.
I'm assuming this is a problem with my MTA, and admittedly I'm a bit unclear as to what else I need to do (though I plead ignorance, and I'm sure it's something simple). I have the aliases properly built (I think) and I have run 'newaliases" after the fact. Everything seems fine in that arena, so seeing as I can post to the lists from a local account, even as an accepted non-member, I assume I have some unforgiving setting in my sendmail config that I cannot find that is bypassing the list filters and requiring moderator approval for every post, including that of the list administrator, which is an account offsite of the host machine.

So, the questions are, 1) is there something simple I need to change in my sendmail.cf? and 2) would it be better to move to exim or postfix (no sendmail love would be lost, I just wanted to learn it). I scoured the list archives and didn't come across this particular question. If someone can link me to something that sends me on my way, I'll be much obliged,
and if there is a more verbose explanation that would be appropriate to share on this list, even more so.

Thanks in advance.

-- warren woodward XMission DSL warrenw@xmission.com (801) 303-0819 (877) XMISSION

"The United States, as the world knows, will never start a war." -JFK, American University, June 10, 1963