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. It's
entirely a matter of statistics, not fundamental design.
I can assure you that in the outside world, the amount of legitimate
mail that comes from no-PTR hosts these days is infinitesimal. It's
one of the filtering rules with the lowest false positive rates.
Other than temporary glitches like the 6-to-4 one, the only place
where I see problems is from auld pharts like us whose mail systems
have been working just fine since the 1980s, and who out of a weird
sort of principle refuse to make changes to bring them in line with
modern practice, even changes that are compatible with equally ancient
STD documents.
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.
Regards,
John Levine, johnl(_at_)iecc(_dot_)com, Primary Perpetrator of "The Internet
for Dummies",
Information Superhighwayman wanna-be, http://www.johnlevine.com, ex-Mayor
"More Wiener schnitzel, please", said Tom, revealingly.
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