YT9TP - Pedja
I've got message from groups.io that mail sent to me is bouncing. Followed the link to check it out.
In Recent Bounces I found out list of bounce notification from several dates all with similar message like this one:
184.108.40.206: 550 Please turn on SMTP Authentication in your mail client. web01.groups.io [220.127.116.11]:53022 is not permitted to relay through this server without authentication.
I checked logs of my mail server and found out no traces of these connections and bounces.
Then I realized that it seems messages are bounced by mail server at 18.104.22.168. That is IP of server where my domain is hosted. Server does have mail server but for this specific domain, MX record is set for different address, meaning mail server at 22.214.171.124 is not used but other one, as specified in MX for this domain.
It seems to me that groups.io occasionally tries to send mail to me using IP address of a domain instead of IP address as specified in MX, and, as expected, that server refuses to accept mail.
As my email is on several groups at groups.io I receive mail from there regularly. It seems groups.io usually properly sends mail using MX information, but occasionally uses domain address instead and then bounce occurres.
I see no way how can I handle such bounces.