On 27 Mar 2013, at 15:24, Berend Hasselman wrote:
It would be really nice if it can be fixed on the list side, assuming it has something to do with the message headers or?
Agree, but I am clueless as to what can cause this.
The correct headers are clearly there, as other clients have no issue threading the discussions (even previous versions of Appleās Mail.app).
Given that only this list is known to be affected, there must be something different, but how would I debug this?