[Dovecot] Seen flag getting lost

[Edgar Fuß]

> You don't have any Thunderbird clients accessing this box do you?
Yes, I have. But I also experienced the problem myself only using mutt and Apple Mail.

>  I have some w[ei]rd issue where our TB with the option
> "don't mark message read", still triggers messages to be marked read
It's the other way round. People read their messages, they are flagged as read and all of a sudden revert to unread.