Mail threads are mixed up what do I do?
This issue seems to go back to 2014! I'm on the latest MacOS version (10.13.4) and the problem exists for me too. I'm not sure when it started, but I'm pretty certain it didn't happen before High Sierra in my case.
This is an incredibly frustrating bug, but just as frustrating that Apple has not fixed it in at least 4 years.
Anyone have a real solution for this one?