Gmail has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication

[andreasdueren]

I got a problem sending emails to gmail. Apparently Cloudron tries to send them via IPv6, even though I have disabled it in the network settings. But even then, I manually set it up but it still doesn't work. Does anyone else have a similar problem?

Failure Reason: Error: 550 5.7.1 [my IPv6] Gmail has detected that this message does not meet IPv6 sending guidelines regarding PTR records and authentication . For more information, go to  https://support.google.com/mail/?p=IPv6AuthError 2adb3069b0e04-5422382618esi2729121e87.370 - gsmtp

The cloudron checks in the E-Mail section are not throwing any errors and neither are external tools. I am not able to recreate this issue on a secondary cloudron instance.