SMTP over IPv6 : gmail classifying lots of IPv6 mail as spam since 20140818

[Laurent GUERBY]

Le Friday 22 August 2014 à 07:16 -0700, Lorenzo Colitti a écrit :
> On Fri, Aug 22, 2014 at 12:56 AM, Laurent GUERBY <laurent at guerby.net>
> wrote:
>         We've been running SMTP over IPv6 with postfix successfully
>         for over a
>         year and since 20140818 gmail.com IPv6 MX started to classify
>         most IPv6
>         sourced emails sent from our machine to @gmail.com as spam.
>         The exact
>         same message sent using IPv4 within one minute of the IPv6
>         bounce is
>         accepted.
>         
>         As there's no way to reach google mailops we had to remove
>         IPv6 from our
>         mail machines and go back to IPv4 only for mail, which is sad.
> 
> 
> Are you following the "Additional guidelines for IPv6" section of
> https://support.google.com/mail/answer/81126 ? 

Hi,

We have reverse and SPF in place so I believe we're following them:

root at lists:~# dig +short TXT lists.tetaneutral.net
"v=spf1 mx a ptr:lists.tetaneutral.net ip4:91.224.149.207 ip6:2a01:6600:8081:cf00::1 -all"
root at lists:~# dig +short -x 2a01:6600:8081:cf00::1
lists.tetaneutral.net.

(The AAAA for lists.tetaneutral.net is currently removed until the
current issue with IPv6 is sorted out.)

I did some statistics in the last few days since 20140818:

IPv6:
root at lists:~# grep gmail-smtp-in /var/log/mail.log|grep ::|grep status=sent|wc -l
236
root at lists:~# grep gmail-smtp-in /var/log/mail.log|grep ::|grep status=bounced|grep "message is likely unsolicited mail"|wc -l
29

IPv4:
root at lists:~# grep gmail-smtp-in /var/log/mail.log|grep -v ::|grep status=sent|wc -l
564
root at lists:~# grep gmail-smtp-in /var/log/mail.log|grep -v ::|grep status=bounced|grep "message is likely unsolicited mail"|wc -l
0

We have another MX out host with similar statistics: about 10-15% of
rejected mails as spam in IPv6 since 20140818 and exactly none in IPv4.

For reference the same statistics on logs before 20140818:

root at lists:~# grep gmail-smtp-in /var/log/mail.log-20140817|grep ::|grep status=sent|wc -l
1135
root at lists:~# grep gmail-smtp-in /var/log/mail.log-20140817|grep ::|grep status=bounced|grep "message is likely unsolicited mail"|wc -l
0
root at lists:~# grep gmail-smtp-in /var/log/mail.log-20140817|grep -v ::|grep status=sent|wc -l
778
root at lists:~# grep gmail-smtp-in /var/log/mail.log-20140817|grep -v ::|grep status=bounced|grep "message is likely unsolicited mail"|wc -l
0

Absolutely zero issue with IPv6 and it has been the case for more than a
year until 20140818.

Note: I changed the subject since it's not "nearly all IPv6 mail" sorry
I did not take time to make some statistics in the first mail.

Sincerely,

Laurent