Zammad does not do that by design.
For you, that behavior would be desirable, for others Zammad should behave as is.
Either merge the tickets manually or you could post a feature request. Has to be configurable though.
That’s not exactly true.
Zammad does automatically merge tickets from the same sender with the exact same subject in a limitted time frame after initial creation.
Hard to tell what’s going and how long the time period in between is.
In my case was 1 hour 30 minutes.
100% same subject, same sender and recipient, only difference in the body is “warning” and “success”.
It´s from a monitoring system mail to our support address.
Try it on a fresh installed zammad. Not working.
It works for someone?
I think this is a basic really important feature.
I doubt that all requirements are met so the function doesn’t trigger. Possibly the mail comes via a different mailbox which may be an issue.
For the other detection methods it’s hard to tell if everything you provided as information “isn’t working”.