comcast ipv6 PTR

Wed Oct 9 17:30:46 UTC 2013

On 9 October 2013 09:58, Andrew Sullivan <asullivan at dyn.com> wrote:
> On Wed, Oct 09, 2013 at 11:35:16AM -0500, Blair Trosper wrote:
>> Does anyone know why (or can someone from Comcast explain why) there is no
>> PTR on their residential/business IPv6 addresses?
>
> Probably because of the considerations in
> http://tools.ietf.org/html/draft-howard-isp-ip6rdns-06.  I seem to
> remember someone showing up in DNSOP one time to argue for a draft
> that the reverse mapping should just be optional under IPv6, but I
> can't lay my hands on the draft.  The last time DNSOP tried to come up
> with recommendations about the reverse tree, the resulting document
> was
> http://tools.ietf.org/html/draft-ietf-dnsop-reverse-mapping-considerations-06.
> It says, roughly, "Well, some peple use the reverse tree and some
> don't.  You might want to think about that, or not."  Despite
> asserting a version of "A or not-A", we were unable to achieve
> consensus, so I think the hope of consistency in the reverse tree is
> not supported by operational evidence.

Yet, apparently, Google has very recently completely stopped accepting
email with no PTR records.

On my Linode over the summer, it seems like this was the first mention
of IPv6 in my errorlog:

Aug 17 03:16:07 (none) dma[7de9.b8dd8ca8]: remote delivery to
gmail-smtp-in.l.google.com [2607:f8b0:400e:c01::1b] failed after final
DATA: 550-5.7.1 [2600:3c01:XXXX::      16] The sender does not meet
basic ipv6 sending#015#012550-5.7.1 guidelines of authentication and
rdns resolution of sending ip.#015#012550-5.7.1 Please
review#015#012550 5.7.1
https://support.google.com/mail/answer/81126for more information.
zo6si1884856pac.170 - gsmtp

Prior to 2013-08-17, most messages were delivered nightly without much
problems (although these cron jobs did often end up in the Spam
folder, and had to be rescued manually); after 2013-08-17, there was
only one nightly message that got through, on 2013-08-26, and
completely nothing since then:

Sep  6 03:15:50 (none) dma[7f00.b9012ca8]: remote delivery to
gmail-smtp-in.l.google.com [2a00:1450:4008:c01::1a] failed after final
DATA: 550-5.7.1 [2600:3c01:XXXX::      16] Our system has detected
that this message#015#012550-5.7.1 does not meet IPv6 sending
guidelines regarding PTR records and#015#012550-5.7.1 authentication.
Please review#015#012550 5.7.1
https://support.google.com/mail/answer/81126 for more information.
qk9si240507bkb.323 - gsmtp

Oct  9 03:15:48 (none) dma[966a.b8dc0ca8]: remote delivery to
gmail-smtp-in.l.google.com [2607:f8b0:400e:c01::1b] failed after final
DATA: 550-5.7.1 [2600:3c01:XXXX::      16] Our system has detected
that this message#015#012550-5.7.1 does not meet IPv6 sending
guidelines regarding PTR records and#015#012550-5.7.1 authentication.
Please review#015#012550-5.7.1
https://support.google.com/mail/?p=ipv6_authentication_error for
more#015#012550 5.7.1 information. vs7si29857999pbc.145 - gsmtp

C.