Mail-loop prevention possible?

I encountered a mailloop between my gitlab-instance and my mailserver. Is there a possibility to prevent this? Is there something like a blacklist where gitlab will never send emails to?

The situation was like this: Gitlab has a dedicated emailadres: which it checks for emails and sends mails from.

Somehow a loop got started where gitlab send an email from to The mailserver then responded: “This emailadres does not exist”, to which gitlab responded: “I don’t understand your message”, to which the mailserver responded: “This emailaddress does not exist”, to which gitlab responded …

Is there a way to prevent this? For now, I restarted gitlab and emptied the mailbox and modified the config-file to have the reply-to-adress changed from to