Anti-Spam solutions

I'm not in charge of our internal IT systems, but our company (with over 20 users) is currently using SpamAssassin on our mail server for filtering. Users currently use Lotus Notes, but ACT! and Outlook are planned to be used.

Since everyone gets pretty different messages, it's hard to tweak SA's filters right. It's extra hard to have to ask our IT guy to do the tweaking, since individuals don't have access. I'd like to use the baysean filtering, but since we can't access the program without our IT guy, it's not really an option.

We don't really want a paid service - although software would be considered. Does anyone have any suggestions for our office?

Thanks!