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

Matija Grabnar matija at
Mon Nov 3 10:51:18 CET 2014

On 11/03/2014 01:52 AM, Lyle Giese wrote:
> If the provider won't or is unable to provide reverse for the IPv6 
> static address you have, it will be sub-optimal for you to continue to 
> advertise and/or use the IPv6 address for SMTP.
> It's all part of the 'prove it's not a dynamic ip address' and part of 
> the 'proper reverse DNS provides some level of authority/delegation to 
> use that ip address for legit SMTP usage'.
My SPF record does exactly that: it provides a level of authority for 
that particular host to send mail for my domain.
In a much better, finer grained delegation, since a PTR maps to a single 
domain, while a SPF specifies exactly *which* domains permit that 
particular host to send mail.

The "need a PTR" requirement was created back when SPF was not even a 
glint in anybody's eye. While I would prefer to have PTR records for all 
my hosts, I don't agree having no PTR merits a clear rejection of a mail 
with a valid SPF record for the host.

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