Gmail unhappy about ip6 settings

Problem Description

It seems that users are unable to send email to gmail addresses becasue of something to do with ip6

Is there a way to switch off the IPv6 part of the mail server?
Or is there a better way to resolve this issue?

Any Error Messages

[ip6 address] Our system has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication.

Please review (incomprehensible pages at an url) for more information


  • Sympl Version [10.0]: 11
  • Sympl Testing Version? [Yes/No] no
  • Debian Version [Buster/Stretch]: bullseye
  • Hardware Type? [Dedicated/Virtual/Pi] dedicated
  • Hosted On? [name of hosting co] mythic beats

For IPv6/modern mail, you need to set a reverse DNS record, which you can do so via the Mythic Beasts control panel - once that’s done and live mail to Gmail (and others) over IPv6 should be fine.

As far as I know, I have done that, but Google was still not happy.

It is possible that there was a time delay involved.

I set the RDNS a day before I had the error reported to me, but it is possible that the error report took a day to reach me, because when I email my own gmail address, it gets through no trouble.

Do you have SPF and DKIM setup correctly? Google is stricter about things like that on IPv6 than on IPv4.

Also, in my experience it seems to take at least a month for Google to recognise a new IP and consider it to be a non-spam sender (as far as I can tell they assume guilty until proven innocent).

Mail Tester is something I use to check SPF, DKIM etc. - it’s intended for mailing lists but works equally well for standard emails:

I found the problem: it was my typo in the DNS.

I had added the IP address of the mail server to the SPF record, but I’d preceded it with ipv6: instead of ip6:

So yesterday evening I spent a happy(?) hour or two changing the SPF record for each domain.

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