spam-assasin on plug server?

Question to the list admins...is the mailing list server running some
sort of spam filter on the incoming mail to all the lists? Reason I ask
is b/c I'm currently spamassasining all incoming mail on my system and
it's an understatement that this is a _very_ CPU intensive task.
If mail is already being filtered at the mailserver, I can move
my procmail rules around to ignore plug-* and not spamassasinate it.
I did that to the linux-kernel list and my load dropped from about 4
to 1.5. :)

~Deepak