On Fri, 28 Mar 2008 15:28:17 -0700 JINMEI wrote: JT/> At Fri, 14 Mar 2008 04:45:00 +0100, JT/> Section 3.2 JT/> JT/> Reports from operators suggest that scoring mail on the basis of JT/> missing or non-matching reverse mapping remains an imperfect but JT/> useful measure of the likelihood that a given message is spam, JT/> particularly in combination with other measures. It is clear that JT/> the presence of reverse mapping, and a match between the forward and JT/> reverse zones, is neither a necessary nor sufficient condition for a JT/> candidate message to be spam. JT/> JT/> I'm not very much comfortable with a statement based on "some people JT/> say something" because it's difficult to assess its validity. In JT/> fact, I cannot really be sure that reverse mapping-based approach is JT/> that effective, considering the fact that most of today's spams are JT/> sent from botnets and the reverse mappings are often provided (when JT/> provided) by the ISP, rather than the end users who host the bots.
But that's exactly _why_ it's effective.. the bots cannot change the ISP's reversing mapping, so a system admin can decide to mark mail coming from dynamic27381.big-isp.example.com as very likely being spam. -- Robert Story SPARTA
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