...it's clean and modular. So your opportunities are (functionally) limitless. You could:

1) Set up a separate SA for such departments.
2) Personalize SA per user, group, what-have-you.
3) Catch addresses, keywords, what-have-you before SA ever gets called.

My solution doesn't uses POP at all. It gets mail from the outside, pipes it through SA, then routes it on to Exchange with no other modifications. Keep in mind that SA by default does not delete anything, and it's not client-based at all.

Quick reply, I know, but I have to get to work! :)