Gmail unhappy about ip6 settings

[hairydog]

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

Environment

• 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

[Kelduum]

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.

[hairydog]

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.

[pwaring]

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:

Newsletters spam test by mail-tester.com

[hairydog]

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.