Woo, Robin just updated K9, my favorite spam filter, to version 1.27. I'm on the mailing list to receive news of updates, and I was reading the update list and thinking "nah, I'll wait to upgrade". But then I got to the line where he said he upgraded the statistics to show two decimal places. Finally! That's a feature I asked for many versions ago 
Now I can tell you that my spam filter is 99.66% accurate over the past ~4700 messages. Pretty good, and I don't even use the DNS blacklist feature (though I do use the regular blacklist to blacklist certain e-mail addresses that anything sent to is guaranteed to be spam -- about 30% of my spam matches my blacklist rules). Well over 80% of my mail is spam. Oh, and no false positives.
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