ipv6-ops Digest, Vol 129, Issue 1

Brzozowski, John John_Brzozowski at Cable.Comcast.com
Tue Jan 12 14:38:31 CET 2016

Bjorn as I mentioned in my other email we will help get this addressed.


-----Original Message-----
<ipv6-ops-bounces+john_brzozowski=cable.comcast.com at lists.cluenet.de> on
behalf of "ipv6-ops-request at lists.cluenet.de"
<ipv6-ops-request at lists.cluenet.de>
Reply-To: "ipv6-ops at lists.cluenet.de" <ipv6-ops at lists.cluenet.de>
Date: Tuesday, January 12, 2016 at 06:00
To: "ipv6-ops at lists.cluenet.de" <ipv6-ops at lists.cluenet.de>
Subject: ipv6-ops Digest, Vol 129, Issue 1

>Date: Tue, 12 Jan 2016 09:35:20 +0100
>From: Bj?rn JACKE <bj at SerNet.DE>
>Subject: Comcast blocking IPv6 subnets at SMTP level
>To: ipv6-ops at lists.cluenet.de
>Message-ID: <20160112083520.GA2012 at SerNet.DE>
>Content-Type: text/plain; charset=iso-8859-1
>did anybody experience issues with Comcast blocking IPv6 addresses at SMTP
>level? We used to be able to send mail to comcast servers but since a
>couple of
>days they cancel SMTP connections with a misleading error message:
># telnet mx2.comcast.net. 25
>Trying 2001:558:fe21:2a::6...
>Connected to mx2.comcast.net.
>Escape character is '^]'.
>554 resimta-ch2-09v.sys.comcast.net comcast ESMTP server not available
>Connection closed by foreign host.
>Forward and reverse DNS etc. is all fine at our site. From other IPv6
>subnets the SMTP connection isn't teminated.
>The KDE project had the same issues last year, see
>I already had a one hour call with a Comcast support guy but their support
>isn't helpful at all, in the end he didn't know what's wrong and the
>result of
>the call with them was zero. Currently it looks like Comcast needs to be
>blacklisted for SMTP if you want to keep sending mails to them reliably.
>that can't really shouldn't be the solution...

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