RE: Last Call: draft-klensin-rfc2821bis

--On Thursday, 27 March, 2008 12:31 -0700 "Hallam-Baker,
Phillip" <pbaker@verisign.com> wrote:

> The key issue here is whether people who rely on AAAA are
> likely to achieve their desired result. Today it does not
> matter because anyone who relies on AAAA alone with no A
> fallback is going to receive almost no mail.

Phillip,

This is true iff you believe that there are too few IPv6-enabled
mail senders to transmit such mail.  It ultimately has nothing
to do with whether there are MX records present, since having an
explicit MX record that pointed to a mail exchanger host that
only had a AAAA record would leave the sender in exactly the
same situation -- deliver over IPv6 or don't deliver at all.
That parallelism moves the discussion entirely out of the scope
of whether the text in rfc2821bis is correct or not.

More important, I suspect that belief is false.   Installations
who run IPv6-only generally know their correspondents.  The
correspondent would presumably need to be running dual-stack, or
have a submission server or equivalent that is running
dual-stack (or IPv6 only as well), but, in many parts of the
world, those are not rare.

A statement I believe would be true is that a mail server that
only supported incoming connections over IPv6 would receive
almost no spam, at least until IPv6 becomes much more popular.
But, the last I heard, that would usually be considered an
advantage.

   john

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