nanog mailing list archives

Re: Our first inbound email via IPv6 (was spam!)


From: Jeroen Massar <jeroen () unfix org>
Date: Tue, 05 Jun 2012 07:33:19 -0700

On 2012-06-05 07:29, Raymond Dijkxhoorn wrote:
[..]
;; ANSWER SECTION:
comcast.net.            358     IN      MX      5 mx3.comcast.net.
comcast.net.            358     IN      MX      10 mx1.comcast.net.
comcast.net.            358     IN      MX      5 mx2.comcast.net.

;; ADDITIONAL SECTION:
mx2.comcast.net.        6958    IN      A       76.96.30.116
mx3.comcast.net.        358     IN      A       68.87.26.147
mx1.comcast.net.        358     IN      AAAA    2001:558:fe14:70::22

You are now only accepting IPv6 if all IPv4 fails?
Or will AAAA records for mx2 and mx3 added later?

Though it can work, it used to be a really bad idea as there where a
couple of SMTP systems (Communigate Pro being one of them I recall)
which just failed when not seeing an "A" on an MX, this as they did not
understand IPv6...

There is bound to be other systems that are broken like that that will
not failover to the secondary MX, as such, you might want to add an IPv4
address there too just in case.

Greets,
 Jeroen


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