[geeks] simple DNS / nslookup question

[Mike Meredith]

On Sun, 2 Dec 2007 11:37:13 -0500 (EST), der Mouse wrote:
> What's wrong with fallback-to-address?  MTAs not doing it, yes, that's
> wrong; that's not how the spec is written.  But - largely because it
> *is* how the spec is written - I can't see anything wrong with mail
> setups that depend on it.

To be honest, I'm not entirely sure. I do know it's not regarded as a
Good Thing amongst at least some mail standards fascists. A quick skim
of RFC974 doesn't seem to show up any mention of fallback-to-address,
although it does imply that pre-MX SMTP would use A records (or
hosts.txt).

I suspect that fallback-to-address was always intended merely as a
migration strategy, and/or a site local thing. Have you any pointers to
the spec that indicates fallback-to-address ? (just curious) Or am I
missing the blindingly obvious in RFC974 :)

Removing fallback-to-address just to comply with standards may well be
taking standards compliance too far. It's not impossible that keeping
fallback-to-address, also keeps some perverse failure modes alive. I'm
not aware of any such failure modes, but I don't presume to think that
they don't exist.

-- 
Mike Meredith (http://zonky.org/)
 "Why are we hiding from the police, daddy?"
 "Because we use vi, son, and they use emacs."