to Marcus: do you using greylisting module with default configuration
or you find some more usefull conf.
I'm thinkig about change filter from spamassassin to greylist. Can you
compare these two mudules?
comparing Spamassassin to greylisting is a bit difficult as the two do
completely different things. I suggest adding greylisting to your
setup in addition to other filtering measures you may employ. Probably
your current configuration employs SA during post-processing but
pythonfilter works before new mail gets accepted for delivery.
Greylisting simply rejects every incoming message and asks the sender
to try again a bit later, SA analyzes the actual content of the
message and tries to discern if it contains unsolicited bulk mail. It
is also possible to use SA in pythonfilter and completely reject any
mail identified as junk instead of just marking it as such but that
makes it much more difficult to deal with false positives.
Regarding my pythonfilter configuration, I'm not really sure if I did
further tweaking but I remember that it wasn't really necessary
because it all worked fine out of the box.