John Levine wrote:
surely we in the IETF should be able to do better than to have our mail
servers filter incoming mail based on completely irrelevant criteria
like whether a PTR lookup succeeds!
Spam filtering is sort of like chemotherapy, the difference between
the good and the bad is pretty small, and the trick is to find
measures that will kill the disease without killing the patient.
the analogy falls apart because in most cases there's no recovery from
a spam filter - if a message it's filtered inappropriately, it's
killed.
It's entirely a matter of statistics, not fundamental design.
strongly disagree. stats can play a part, but there's no substitute
for well-chosen criteria. (it would help immensely if spam filter
writers actually understood statistics.)
I can assure you that in the outside world, the amount of legitimate
mail that comes from no-PTR hosts these days is infinitesimal.
in large part that's because poorly chosen spam filters have "trained"
mail senders (legitimate and spammer alike) to set up PTR records.
basically the hoops become meaningless. and IPv6 is a different enough
case that the old assumptions should not be presumed to be valid.
So, yeah, spam stinks, but it's not going away, and arguments that you
shouldn't use a technique today because it didn't work in 1998 don't
cut it.
that's hardly a justification for stupidity.
Keith
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