Re: [Asrg] Fallback to MX

John Levine <> Fri, 12 February 2010 20:34 UTC

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Date: 12 Feb 2010 20:35:52 -0000
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From: John Levine <>
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Subject: Re: [Asrg] Fallback to MX
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>> I have a theory that you will never, ever, have any reason to accept
>> mail from IPv6 networks, since everyone you want to hear from will
>> have an MTA or gateway on IPv4, but that is a separate argument.

>Never's a long time.  I think you might be right, but only because I
>expect Internet governance to implode before 6 overtakes 4 as the
>default IP version.  If not for that, I would expect IPv6 to reach a
>point where IPv4 is but a quaint curiosity within times I can
>reasonably expect to live to see - say, the next 30 years.

Given the incredibly botched way IPv6 has been rolled out, e.g., DHCP
still doesn't work, I expect we'll be seeing a lot of it within
networks, but with 6to4 NATs to talk to the rest of the world for a
long time.  Unless v4 goes away completely, there's no disadvantage to
sending it through 6to4, since mail, unlike a lot of other
applications is designed to be proxied and relayed.