unable to send emails to gmail

[nostrdev-com]

We are running v8.2.3 (Ubuntu 22.04.3 LTS) on a Hetzner dedicated machine. Email works fine EXCEPT when sending to gmail addresses. Error message as follows:

Failure Reason: Error: 550 5.7.25 [2a01:4f9:6b:3643::2] The IP address sending this message does not 5.7.25 have a PTR record setup, or the corresponding forward DNS entry does 5.7.25 not match the sending IP. As a policy, Gmail does not accept 5.7.25 messages from IPs with missing PTR records. For more information, go 5.7.25 to 5.7.25 https://support.google.com/a?p=sender-guidelines-ip 5.7.25 To learn more about Gmail requirements for bulk senders, visit 5.7.25 https://support.google.com/a?p=sender-guidelines. 2adb3069b0e04-5439af119basi4274713e87.169 - gsmtp

This has been going on for at least a couple of weeks. Redoing the DNS entries did not help.

[nostrdev-com]

Looks like this part does fix it (instructions for root server):

Thanks to you both for the pointers!

[BrutalBirdie]

Forum Search with similar issues:

• https://forum.cloudron.io/topic/13072/gmail-ipv6-anyone-else-with-this-experience
• https://forum.cloudron.io/topic/13122/email-sending-broken-after-updating-to-8-2-x-due-to-ipv6-issues

Did you check this out?

[jdaviescoates]

and this one https://forum.cloudron.io/topic/13145/problems-with-sending-mail/4?_=1737490852861

In short:

1. Set-up PTR records for IPv6 (see https://forum.cloudron.io/post/99971 )
2. in Network: under IPv6 section I chose Public IP (was previously Disabled)
3. in Domains -> hit Sync DNS (for good measure)

Should do the trick. Although I think maybe @avatar1024 has also been having issues with gmail even after doing all that?

[nostrdev-com]

Looks like this part does fix it (instructions for root server):

Thanks to you both for the pointers!