> It is also not very useful from the MTA point of view, since the MTA can't
> tell if A or AAAA records are missing because they don't exist or there
> wasn't enough space in the DNS reply etc. So in most cases (especially an
> IPv6 aware MTA getting no AAAA records in reply) the MTA still has to
> follow up an MX query with more queries to get address records.

Sounds like an AORAAAA record with flag bits would help there, too, so
long as the authoritative server returned it in the addition section.  The
client asks for the MX, and gets the AORAAAA so it doesn't have to do A or
AAAA requests separately.

Alternate grosse hackque: some way to return an anti-result in the
additional section that says there are no records of this type for this
name, that can be negative cached.

Regards,
John Levine, johnl@taug..., Taughannock Networks, Trumansburg NY
"I dropped the toothpaste", said Tom, crestfallenly.
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