Change string after the @ in the message-id

[labdir]

How can permanently change the "cerb" string after the at sign in the message-id? That's case is from version 11.0, in previous version was the Swiftmailer still used. Ideally the domain from the mail address is used after the at sign. This causes the fewest problems with delivery through spam filters.

[Hildy]

It's not configurable through the UI; you'd need to modify the code to do that. That header is also used for Relay authentication, so if you use worker relaying, it might break that unless modified accordingly.