On 2023-06-16 at 13:37:19 UTC-0400 (Fri, 16 Jun 2023 13:37:19 -0400) John Possidente via mailop <possiden...@gmail.com> is rumored to have said:
> A sender of legally mandated bulk mail who are very conscious of making > sure they're dotting every i and crossing every t (because they're required > to) asked me today whether port 25 pingback is still necessary. I > immediately thought, "Of course not," but on second thought (before > speaking, yay) realized that maybe I'm wrong. > > Does anyplace still reject mail from sources that don't answer on port 25? Do you mean this literally in a technical sense, i.e. that the SMTP client IP must accept a port 25 connection back to it? I'm not aware of that EVER being a usable tactic that would be worth adapting to. Those people do not want their mail. In the logical sense of "does the domain part of the SMTP sender address have appropriate A/AAAA/MX records in DNS that could make a bounce feasible?" there are very many places enforcing that, as they should. If the envelope sender address is not even theoretically mailable (i.e. hard app-layerfailure from DNS) one can expect the mail to be rejected or in some cases intentionally blackholed after acceptance. In between would be full SMTP callback verification, testing whether the sender will accept mail from '<>' in real time, synchronously with the original offer of mail. This has been MOSTLY abandoned because it predictably results in false positives and has become increasingly risky to the checker's reputation and error-prone over the years. A "legally mandated" sender should probably expect some of that to still be in use, because the long tail of mail admin incompetence is a thing... -- Bill Cole b...@scconsult.com or billc...@apache.org (AKA @grumpybozo and many *@billmail.scconsult.com addresses) Not Currently Available For Hire _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
