Spamhaus ZEN: 80% blocking rate, zero false positives

As reported yesterday in Al Iverson's SpamResource web page:

Iverson was becoming overwhelmed by the spam sent to his abuse address. For obvious reasons, it's a very bad idea to filter an abuse-reporting address because legitimate abuse reports are too easily mistaken for spam.

As an experiment, Iverson applied the the Spamhaus ZEN blocking list to his incoming abuse mail — to tag rather than block.

(Spamhaus ZEN is a merger of the three blocking lists maintained by Spamhaus, and thus should be the most aggressive of them all.)

Iverson's results: out of over 2200 spams received in February so far, nearly 80% would have been blocked by Spamhaus, and there were zero, none, nada false positives.

This is encouraging news for administrators who worry if it's safe to use a blocking list. More testing is required though before it's safe to give Spamhaus the Zero False Positives Seal of Approval. At the very least, we need to see results from a variety of different users, and we need to see the results applied to a corpus of many more than 2200 messages.