Implicit MX and A RRs (was: Re: Last Call: draft-klensin-rfc2821bis)

--On Wednesday, 26 March, 2008 22:41 +1100 Mark Andrews
<Mark_Andrews@isc.org> wrote:

>...
>> It would be needed until IPv6 takes over.
> 
> 	It will be needed even *after* IPv6 takes over.  There will
> 	be lots of queries for A records long after the majority
> 	of hosts don't have A records.
> 
> 	We need to remove the implict MX from A to prevent the A
> 	record lookups occuring as things currently stand.

Mark,

Whether that proposal is a good one or a bad one, it can't be
done in 2821bis because that is a document moving from Proposed
to Draft Standard and the implicit MX feature is _very_ widely
deployed and used.  So, IMO, this discussion is not directly
relevant to the (already closed) Last Call on 2821bis and should
probably be move to the ietf-smtp mailing list.

Second, no matter what is done with standardization, it will be
many, many years before one could count on those A RR lookups
not occurring -- too much software out that that is very rarely
updated.   The advantage of the "MX 0 ." approach over getting
rid of the implicit MX from A is that, if there were consensus
for it, it can be deployed in less than geological time.

But, either way, it seems to me that the correct (and only
feasible) actions start with an I-D that says something useful
and is discussed on, at least, the ietf-smtp list.

Just my opinion, of course.
   john

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