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Re: Registration model, 2821bis-06

2008-04-02 12:17:08

--On Wednesday, April 02, 2008 11:01 AM -0700 ned+ietf-smtp(_at_)mrochek(_dot_)com wrote:

Connectivity to/from AAAA-only mail servers will suck
terribly for many decades to come, but no 2821bis
wordsmithing can avoid that. Only an arrangement with a
dual-stack relay can improve connectivity, and that
practically requires an MX RR or more.

This is certainly true for the Internet email service. But not
all use of
standardized email protocols (including usage on the open
Internet) is in
futherance of this service. It is entirely possible that at
some point
an alternate service offering will emerge that's IPv6-only. I
have no idea
how likely this is but it is not beyond the realm of

And, in addition and FWIW, the claim that a dual stack setup "practically requires" an MX setup is false, as has been pointed out before. The following setup, with no MX record, is all that is necessary under the current 2821 standard: IN A ...
                           IN AAAA ....

That would cause, regardless of how this argument about AAAA-based synthesis comes out, an implicit MX record equivalent to IN MX 0
to be generated and then address selection algorithms specified elsewhere to be used.

If one had stronger preferences about which interface type was preferred, one could use MX records to specify that. But that has been the case for a long time and none of these proposals or options changes that.

One can sensibly argue that the flexibility about address (actually interface) selection is too broad and could be tightened. But that, too, is a major new piece of work.

And, like Ned, I'm tiring of repeating myself about this.


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