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Re: I-D Action:draft-klensin-rfc2821bis-10.txt

2008-04-16 07:52:05

On Tue, 15 Apr 2008, Arnt Gulbrandsen wrote:

Exim users can comply by disabling the sender_verify variable

That's a version 3 option so it hasn't been supported for many years.
If Exim 4 is compiled to support IPv6 then it will accept AAAA-only
addresses, though you can disable this on IPv4-only hosts.

I doubt that it makes sense to accept email from 
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. (I freely admit I'm extrapolating here given the extremely
limited amount of production deployment of IPv6 at present, but I'd be
surprised if this didn't end up happening after seeing how IPv4-only setups