Read mails (trashbin) won't sync read status

[chfilm]

Hey,
so since Mac OS 15 I noticed a weird behaviour.
During the day I'm reading and deleting mails on my iphone or mac studio at the office.
But when I come home to my macbook- I see let's say 50 unread mails in my trashbin. Somehow, the read-status is not being synced anymore.

I use a third party mailserver (domainfactory). Any ideas?

 

[GlenK]

I use Mac Mail and the same thing is happening. I think some of them are just changing back to unread after being marked read on the Mac (Studio). I'm checking that now..

Update: No mine is the same not syncing error. They are not changing back to read from unread.