On Wed, Apr 16, 2008 at 04:45:07PM -0400, John C Klensin wrote: > --On Wednesday, 16 April, 2008 14:31 -0600 Willie Gillespie > <[EMAIL PROTECTED]> wrote: > > > Tony Finch wrote: > >> On Wed, 16 Apr 2008, Ned Freed wrote: > >>>> I doubt that it makes sense to accept email from > >>>> [EMAIL PROTECTED] on a system that can only > >>>> communicate with IPv4 addresses. > > > > I foresee some company setting up an IPv6 to IPv4 e-mail relay > > for individuals or other companies that only have IPv6 > > addresses. > > Very likely, IMO > > > For an IPv4-only receiving system, would this appear as an > > e-mail from [EMAIL PROTECTED] (even though it comes over > > the IPv4 link)? At that point, would it make sense to accept > > the message? > > Sure. The problem arises if the receiving IPv4 host tries to do > some sort of sender-accessibility or callback verification. It > won't be able to reach the IPv6 host (or send NDNs to it) unless > it either it is configured to submit those messages via an > IPv6-capable gateway or the IPv6 host advertises IPv4 addresses > (perhaps via a conversion relay in a low-preference MX record).
Translated: The host needs an A record, or an MX record which points to at least one A record. There's no point in relying its AAAA record to act as an implicit MX record, not as long as there are hosts out there which have no clue about IPv6. >From my perspective, you agree with: > Date: Sat, 5 Apr 2008 14:26:50 +0200 > From: Alex van den Bogaerdt <[EMAIL PROTECTED]> > To: [email protected] > Subject: Why implicit MX is a bad idea for IPv6 > Message-ID: <[EMAIL PROTECTED]>
