Hi all,
My very strong opinion is that the zero-preference-MX rule must still
stand, regardless of how to tackle the domain-owners' problem. It's law.
It's also often useful, especially when the DNS administrator isn't handy
and you want mail service on a single public host, especially on a
temporary basis. (It's amusing to think that, now that MX records are the
commonality for which a transition plan was provided for non-users when
first introduced, spammers often don't spam hosts without them because of
their near-universal ubiquity.)
It doesn't matter what itch needs to be scratched to make MX or DNS usage
perfect; taking the rule away is _going to break compatibility with old
clients_. And that's all. When MX records were introduced, we would
never have dreamed of doing a thing like that. So why are we even
contemplating it now? (I think I've caught up with all of the discussion
so far, but please point me to anything if it's already been answered.)
To address the problem that begs for the rule's removal, however: how
about a fake MX that rejects everything as the draft-rfc2821-bis allows
with the 554 code on connection opening? How about not minding that the
sending host is the one with the problem, and not you (not nice, so it'd
be good to sort it out)? How about using a known-nonexistent (EG:
definitely.invalid) host as your MX target (has more bad effects than
known behaviour but at least it works - and when the rules don't allow us
to do better than that for now, that's all we can hope for)? This "MX 0
." sounds good as well, because it only requires time for implementers to
get the idea and implement it while it's a bit of bother in the meantime.
So no, please don't drop that rule. It's very handy, anyway, even if it
is an irritating little blister just yearning to be popped, both to make
semantics and practice clean and current for DNS and SMTP. But we spent
ages making the MX record what it is - a record for indicating the names
and preferences of mail exchangers, with a known behaviour for absent MX
records. Changing the meaning of MX from being just a preference list to
an actual indicator of whether mail is wanted or not would not have made
sense at the time, and I feel strongly that it still hasn't got even the
slightest motive for doing so today when practical and long-term solutions
that can work without breaking compatibility seem possible with the
minimum of badness.
Cheers,
Sabahattin
--
Sabahattin Gucukoglu <mail<at>sabahattin<dash>gucukoglu<dot>com>
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