It's pretty easy to stop messages with null characters if you use Mimedefang, a milter. A built-in function called SuspiciousCharsInBody tags messages with either nulls or bare CR or LF. We've let this go but since we're testing a Cyrus server it looked like we should stop them coming in.
We started rejecting them about 5 hours ago and it's a remarkably effective spam filter. It got about 9,000 so far. There might be a legit message in there but I can't see one, just eyeballing the subject lines. It gets a lot of Chinese porn spam, and also pirate software, Viagra ads, bank phishing, etc. I cannot tell how many had nulls and how many had bare CR and LF so this might be tangential to the null discussion. But certainly legit mail with nulls appears to be very rare.
Joseph Brennan Academic Information Systems Columbia University in the City of New York
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