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Re: [ietf-smtp] EHLO domain validation requirement in RFC 5321

2020-09-27 10:40:44
I would say instead that because some subset of inbound MTAs do EHLO verification, "real mail servers" (i.e. those which manage to continue to deliver mail with some reliability) are forced to have static IPv4 source addresses for which PTR lookup results match EHLO arguments.

No, we've observed in practice that hosts that don't have matching PTRs are spambots.

Anything that comes from a dynamic or NAT pool is invariably spam from a botnet.

No, because nobody is looking that closely.

Sorry, but you're just wrong. We absolutely look that closely. I know people who maintain pools of patterns to recognize dynamic pool rDNS which lots of people use in their spam scoring.

It would be nice if mail still worked the way it did 30 years ago, but that was most definitely then, and this is now.

John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
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