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

2020-09-27 15:30:50
John C Klensin writes:

regional registries.  Independent of clients who are part of
clouds and business arrangements large enough to push ISPs
around, many ISPs refuse to create reverse mapping records at
all [1] or will not create ones that that match client
perceptions of their names rather than server-location based
names following the ITU model [2]/

[1] As handy examples pulled from this thread, and apparently have no reverse mapping records at all.


;; AUTHORITY SECTION:    71418   IN      NS    71418   IN      NS    71418   IN      NS

The somewhat cumbersome verified that it's not just the little bubble of the Intertubes that I live in can see this reverse mapping.

Anyway, the only point I made is that I believe that the MUST NOT, when it comes to EHLO/HELO validation, is frequently ignored in practice. Those who are of the opinion that validation is bad practice, nobody will force them to do it. And those who do believe that it filters out a bunch of crap will do it; they will ignore the MUST NOT. That's it.

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