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

[Matija Grabnar]

On 11/02/2014 06:55 PM, Darren Pilgrim wrote:
> On 8/22/2014 2:46 AM, Matija Grabnar wrote:
>> So, much as I would LIKE to have reverse IPv6 DNS on my mail servers, in
>> some cases it is just not possible.
>
> Can you describe those cases?  I can't think of any scenarios where 
> you'd run a correctly-configured public MX and not have reverse DNS.
Bah - I have a correctly configured public MX on my home network (static 
IPv4, static IPv6). It's correctly configured, but I have been as of now 
unable to convince my provider to delegate reverse DNS (for IPv6) to my 
DNS. They are simply not set up for that. Otherwise, the MX is 
completely correctly configured. Under IPv4 it even has a PTR (for the 
lone static IPv4 address).

And I've had similar problems ("we are not set up to delegate reverse 
DNS for IPV6") with a hosting provider. I had a suggestion on the list 
that I should simply rehost my machines, but alas it is not practical, 
since the provider was chosen for a bunch of other parameters (bandwidth 
cost, hosting cost, etc), with IPv6 connectivity an afterthought.

It is completely possible to have a "correctly configured public MX" and 
not have a reverse DNS - unless your definition of "correctly configured 
public MX" demands a reverse DNS, but I assume you wouldn't insult both 
our intelligences with a "no true scotsman" fallacy of that sort.