Tony Finch wrote:
On Thu, 22 May 2008, John Levine wrote:
Personally, I think it's severe mission creep to try to define an
existence check. It's straightforward to check for a NXDOMAIN or
NODATA result, but I see no reason to think that such a check has the
semantics an ADSP user would want.
NODATA is even more wrong than NXDOMAIN :-(
Definitely, which is largely the reason why I feel this needs to be
specified in ADSP.
I agree that checking for the existence of MX, A, and/or AAAA records is
a better approximation to those domains that use email than is mere
existence (lack of NXDOMAIN). There will of course be domains having A
or AAAA records that don't use email, so even if we do the better check
we don't know for sure that the From address is valid, although they
could still publish an ADSP record.
But the NXDOMAIN check is attractive in its simplicity, and it does
cover the case where it isn't possible to publish an ADSP record (since
the domain would then exist).
My question: How many domains exist that don't have MX, A, and/or AAAA
records? Is the additional coverage of these domains important, or is
the NXDOMAIN check good enough?
-Jim
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