4 ms·

Gmail blocks my mailserver, I recently discovered it’s the lack of ipv6 that causes it.

jedberg 6y ago
If your mail server is in AWS, it's not ipv6 that is the problem per se. It's that google has blocked the entire AWS address space. To be fair, you shouldn't be sending email from AWS without going through SES, which has it's own address space and has specific deals for deliverability to all the big mail recipients, like gmail and hotmail.
- Bnshsysjab 6y ago
  AWS allows you to switch mail servers to a specific address range which, as far as I know, are treated nicer than the regular address space. Please provide citations if you’re going to speak so factually.
  - jedberg 6y ago
    > Please provide citations if you’re going to speak so factually. That's fair. I don't really have handy citations. I just know this stuff from working in email deliverability for a long time. I guess you can choose to believe me or not.
    - Bnshsysjab 6y ago
      I have a DigitalOcean mailserver that isn’t blocked by google, or o365 ;)
jlokier 6y ago
I had the opposite problem. A mailserver was blocked by Gmail until I disabled IPv6 on it.
- Bnshsysjab 6y ago
  Interesting. I imagine it may be ips sitting in a pool which are known bad in your case, and in mine known good slightly tipping the black box scales. I just wish gmail had tech support so I could resolve this directly instead of flailing about trying random obscure solutions.
  - jlokier 6y ago
    In my case, the messages from Gmail's MX suggest the problem was reverse DNS for the EHLO name returning the IPv4, for a connection from the IPv6. I decided I'd need to configure Exim4 to issue a different EHLO name depending on whether it's connecting over IPv4 or IPv6, and then triple check (with tests) that reverse DNS unambiguously matched in each case. But as deliverability was the priority, disabling IPv6 seemed lower risk than fiddling with config, seeing it work, then finding out a few weeks later that it introduced another "Google mystery factor". Reviewing that is on the todo list somewhere, very low priority.

If your mail server is in AWS, it's not ipv6 that is the problem per se. It's that google has blocked the entire AWS address space. To be fair, you shouldn't be sending email from AWS without going through SES, which has it's own address space and has specific deals for deliverability to all the big mail recipients, like gmail and hotmail.

Bnshsysjab 6y ago
AWS allows you to switch mail servers to a specific address range which, as far as I know, are treated nicer than the regular address space. Please provide citations if you’re going to speak so factually.
- jedberg 6y ago
  > Please provide citations if you’re going to speak so factually. That's fair. I don't really have handy citations. I just know this stuff from working in email deliverability for a long time. I guess you can choose to believe me or not.
  - Bnshsysjab 6y ago
    I have a DigitalOcean mailserver that isn’t blocked by google, or o365 ;)

jlokier 6y ago

I had the opposite problem. A mailserver was blocked by Gmail until I disabled IPv6 on it.

Bnshsysjab 6y ago
Interesting. I imagine it may be ips sitting in a pool which are known bad in your case, and in mine known good slightly tipping the black box scales. I just wish gmail had tech support so I could resolve this directly instead of flailing about trying random obscure solutions.
- jlokier 6y ago
  In my case, the messages from Gmail's MX suggest the problem was reverse DNS for the EHLO name returning the IPv4, for a connection from the IPv6. I decided I'd need to configure Exim4 to issue a different EHLO name depending on whether it's connecting over IPv4 or IPv6, and then triple check (with tests) that reverse DNS unambiguously matched in each case. But as deliverability was the priority, disabling IPv6 seemed lower risk than fiddling with config, seeing it work, then finding out a few weeks later that it introduced another "Google mystery factor". Reviewing that is on the todo list somewhere, very low priority.