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

Lorenzo Colitti lorenzo at
Fri Aug 22 16:32:41 CEST 2014

On Fri, Aug 22, 2014 at 7:24 AM, Nick Hilliard <nick at> wrote:

> On 22/08/2014 15:16, Lorenzo Colitti wrote:
>> Are you following the "Additional guidelines for IPv6" section of
>> ?
> it looks like Google is trying to enforce SPF / DKIM on ipv6 connections
> where there is no similar requirement for ipv4.  Is there a particular
> reason for this?  It's causing a lot of breakage.

I believe the answer has to do with the fact that a lot of IPv6 email is
spam and the fact that if you can't/won't do what's suggested in the
"additional guidelines for IPv6" then you can always continue to use IPv4.
>From what I've heard it's somewhat of a consensus position among large
email operators on what to do for IPv6 SMTP inbound.

Note that from the text it sounds like SPF / DKIM is not strictly required,
but it looks like a PTR record is a hard requirement.
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