Sometimes when I send from my server, I get the following response from Gmail (IP masked by me)

: host aspmx.l.google.com[2a00:1450:4013:c00::1a]
said: 550-5.7.1 [2a01:**:**:**::2      12] Our system has detected that
this 550-5.7.1 message is likely unsolicited mail. To reduce the amount of
spam sent 550-5.7.1 to Gmail, this message has been blocked. Please visit
550-5.7.1 http://support.google.com/mail/bin/answer.py?hl=en&answer=188131
for 550 5.7.1 more information. hm5si113822760wjb.117 - gsmtp (in reply to
end of DATA command)

Some people recommended to disable IPv6 for Gmail. But google seems to miss an IPv6 PTR entry in the DNS. I found some help on this, but all this stuff is a bit above my head.

To my understanding I just have to create a PTR record for instance with the help of this tool and add that to my DNS record.

Is it that simple?

edit Some links to the Problem.

  • 1
    If you want a reverse DNS record, you’ll have to ask your server provider to generate it. My server has been running IPv6 for years now and I never had any problems with rejected mails.
    – Daniel B
    Jan 6, 2015 at 12:45
  • The reason Google believes its spam has nothing to do with it being IPv6 but everything to do with the DNS record not existing. Furthermore the information you quoted indicates that Google itself is using a IPv6 address.
    – Ramhound
    Jan 6, 2015 at 12:55
  • @DanielB I have control over the DNS entry myself. I just want to know if the process is correct and that simple (because I've read many complicated things about this problem).
    – Mathias
    Jan 6, 2015 at 12:59
  • 1
    No, you don’t. Reverse DNS zones are controlled by the IP owners. Which is not you, but your provider. The only exception is if you have the reverse zone delegated.
    – Daniel B
    Jan 6, 2015 at 13:25
  • Check this out: allaboutspam.com/email-server-test This helped me fixing gmail problems :)
    – Martijn
    Jan 9, 2015 at 8:02

1 Answer 1


The PTR generator tool you linked to seems to generate the correct information for an ipv6 PTR record. I would add that, and probably an SPF record if you do not have one already. That should improve your reputation and increase the likelihood of delivery to Gmail and other mail hosts. As others mentioned, it is not to do with ipv6 at all.

There is an SPF generator, similar to the PTR one at http://www.spfwizard.net/


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