On Wed, 16 Apr 2008, Ned Freed wrote:
I doubt that it makes sense to accept email from
test(_at_)ipv6(_dot_)l(_dot_)google(_dot_)com
on a system that can only communicate with IPv4 addresses.
In a single system case with fully symmetric routing, perhaps not. But as I
mentioned previously, there are many cases where multiple systems with highly
asymmetric routing are used to provide a mail service. In such a setup it is
entirely possible that a system hosting an inbound MTA would have DNS query
access but no outbound IPv6 access even if such access exists somewhere else
in the setup.
Of course, but in that case the postmaster would know that it is possible
to communicate indirectly with IPv6 addresses and would therefore not
disable IPv6 DNS lookup support.
Tony.
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