We make extensive use of the Spam Filter's Blacklists by increasing spam scores by 0.1 for each occurence on a DIFFERENT list (it reduces the number of false positives - the more lists an IP is on, the more likely it receives a higher spam score, adding more weight to some lists than others) and we ALSO use it with whitelists (by assigning a NEGATIVE score - which works like a charm.

However these are IP based lists. It would be helpful if RHSBL are also supported -- and even better if Kerio Connect could figure out by itself what kind of list it is.