Dnia 30.01.2025 o godz. 14:03:51 Matus UHLAR - fantomas via mailop pisze: > Nowadays, we can mark domains that don't send mail using Null MX (rfc 7505). > > But this needs explicit record to say "this domain does not send/receive > e-mail" > > Requiring MX to explicitly state "this domain does send/receive > mail" would clean up field a bit.
Consider a classical scenario (may be an university, as this model was very common in universities): there is a domain example.org, which does not have an A/AAAA record on its own, and there are many servers within this domain (often having "funny" names - university people like it: frodo.example.org, gandalf.example.org, rabbit.example.org, alice.example.org etc.) Each of these servers runs a MTA - you may think of it as of each university department having their own mail server (which is also very common in universities: each department has their own rules for doing things and they cannot accept to be put under one single "government"). All these hosts have A/AAAA entries in the university's DNS server, and these names are used in email addresses when sending/receiving mail to/from particular department. If someone at host "frodo" wants to mail someone at host "gandalf", they just address the message as "user@gandalf" (the mail software is usually configured so that they don't need to put the full domain name into address - .example.org is appended automatically if they use just bare hostname). Do you really think it's reasonable to put MX records for all these machines into the DNS, that basically duplicate the A/AAAA records? What for? For me similar scenario (multiple hosts in a network and mail exchanged between these hosts) was always a strong proof that the fallback to A/AAAA should and must remain. Actually, I never considered this as "fallback", I always thought of it as a *primary* form of an email address - email address has the form username@host, *unless* there is a MX record, then you can use username@domain. In this classical scenario "domain" would be just example.org - the parent domain for all these host names - which does not have the A/AAAA record on its own, but has a MX record that points to one of the hosts within example.org. The MX host is responsible for redirecting the mail to other hosts within the domain, if applicable. Thus, you can mail to just u...@example.org without having to remember at what host within example.org the user does have the account (but you *can* send to particular host if you want). And that MX host usually just forwards the messages - using some alias table - to u...@somehost.example.org, without needing to have an additional MX record for somehost.example.org. Yes, I do have MX record for rafa.eu.org that points just to rafa.eu.org, which in my opinion is stupid. I did this because in the past some stupid antispam systems tended to assign me some negative score because of not having a MX. But I still think in cases like mine just A/AAAA *should* be fully sufficient. -- Regards, Jaroslaw Rafa r...@rafa.eu.org -- "In a million years, when kids go to school, they're gonna know: once there was a Hushpuppy, and she lived with her daddy in the Bathtub." _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
