I just installed Real Time Blacklist into the smtpfront on qmail. I can't believe the results. At least a 70% drop in spam getting into the system.
I am using the RBL's from spamhaus, njabl and ignorant.
So far no ham has been rejected, so we might add a few of the more aggressive lists.
This system beats spamassassin, primarily because it seems to take a lot less processor time (under 1% versus 17 to 24% for assassin) and you don't have to deal with all the trash that builds up on the servers drives. (You would figure that these drives would grow on their own with a the v-iaagR_a ads they get).
Now that I've done it the only question I have is why didn't I try this earlier and why doesn't everyone running qmail or sendmail do it?