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    In a perfect world, your DNS server implementation would not allow, or at least require you to explicitly acknowledge, non-compliant configurations.

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      It is interesting mail is the only service to get its own explicit record type. Modern protocols like XMPP will use either SRV or TXT records.

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        MX was basically the first SRV record type, and then after that they went “we should really make a general case tool for this”.

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          It helps that mail predated DNS. DNS was standardised in 1983, SMTP (which wasn’t the first email protocol) was standardised in 1982.

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            Yes, modern services don’t get their own DNS RR, but plenty services have: https://en.m.wikipedia.org/wiki/List_of_DNS_record_types

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            My years running Courier taught me this. I’m surprised that there are still 6,000 600 domains in the top million that are incorrectly configured without realizing it.

            Edit: mfw

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              600 :-)