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Our current blacklists...
- sbl.spamhaus.org
- spam.dnsrbl.net
- dun.dnsrbl.net
- list.dsbl.org
- bl.spamcop.net
The first three take a very conservative approach. dsbl is aggressive by comparison, but is still far more conservative than a "spews" type of list. The fifth position on our list is where we try out more aggressive blacklists, and see how many false positives (FPs) they generate over a short trial period. That spot is occupied by SpamCop now, and has been for a while... they generate a handful of FPs, but so far it has been within acceptable limits for our users.
The fact that SpamFilter checks blacklists in the listed order means that "hit rate" is always going to be weighted heavily toward the first blacklists in the list. And that's actually a good thing. By ordering the blacklists according to their listing policies -- the more conservative blacklists at the top, the aggressive lists at the bottom -- it makes it much easier to test for FPs. If our top blacklist SpamHaus says it's spam, you can bet your paycheck on it. The remaining hits on the more aggressive blacklists near the bottom of the list can then be more easily evaluated for FPs.
In the past, I tried out another blacklist...
This blacklist blocks legitimate opt-in ad mail, but flowgo is one of those companies that makes opt-in look bad. The user ends up with far more mail than they expected. Flowgo does have a legitimate, working unsubscribe capability... but we just got through training our users to NEVER click on "unsubscribe" links, and quite honestly, they can't always tell a flowgo ad from the rest.
My only reason for removing the flowgoaway blacklist lately is that it has become much less effective now than it was even just a few months ago. Don't know why.
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