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> I see there's a RDNS_NONE rule for when the sending IP address has no DNS
> PTR (reverse DNS) record. But no rule for when that PTR record doesn't
> have a matching A (forward DNS) record that matches the sending IP?
> Is this something that would be accepted into spamassassin if I created a
> module? Or a feature that would be added if I didn't do it?
There are legit mail servers with bad DNS. Not the big ISPs or hosting
companies, but small businesses and nonprofits sometimes get this wrong,
and in a few countries nonmatching records seem to be routine. We've
considered blocking for it, but we'd end up doing a lot of whitelisting
and interfering with mail that our users want.
It's worth scoring for, and RDNS_NONE already matches this case.
Lead Email Systems Engineer
Columbia University Information Technology