SMTP over IPv6 : gmail classifying nearly all IPv6 mail as spam since 20140818

Matthew Huff mhuff at
Sat Aug 23 17:52:40 CEST 2014

Nick, I would expect the response will be silence. Since the current RBL methods are not currently operational with IPv6 due to design issues and that IPv4 reputation is a large part of anti-spam, there is a fundamental difference currently between the two protocols. As IPv6 smtp ramps up, I would expect more to move to Googles direction than vice versa. The idea that you will be able to send email from an IPv6 address without rDNS, SPF and DKIM and have it end up in anything other than the spam folder is a pipe dream. Hell, I helped a friend that was running a hosted domain with only IPv4 and he had difficulty getting email delivered to corporate emails systems without SPF/DKIM. The SMTP world is changing, I doubt it is going to go back.

-----Original Message-----
From: at [ at] On Behalf Of Nick Hilliard
Sent: Saturday, August 23, 2014 11:37 AM
To: Lorenzo Colitti
Cc: IPv6 Ops list; Marco d'Itri; Jared Mauch
Subject: Re: SMTP over IPv6 : gmail classifying nearly all IPv6 mail as spam since 20140818

On 22 Aug 2014, at 20:26, Lorenzo Colitti <lorenzo at> wrote:
> What specifically would you like me to pass on? "Dear gmail team, can you please publicly present data on IPv4 spam vs IPv6 spam in order to justify your documented policy?" ?

How about: "Dear gmail team, v6 mta operators have noticed that there is a substantial difference between how spam detection is handled for ipv4 and ipv6 connections and this appears to be causing problems with high rates of false positives on v6 sessions. These problems appear to be specific to gmail and are not seen with connections to other major mail operators. Where SPF/dkim are not feasible/possible, this causes people to either implement gmail specific hacks or else disable ipv6. Both these workarounds act against the interests of both Google and the internet at large. Can you please reach out to the ipv6 operator community about this?"



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