Remove unread message icon from the top bar when you delete a message instead of reading it.

[tanksaretanky]

I got an obvious spam message and deleted it instead of reading it but the unread message envelope didn't go away from the top bar until I went into the trash bin and read it.

 

[Ecclesia]

For me the notification is still there even though I did read the message, the message isn't in the bin either.

 

[ABCsOfLife]

Staff have mentioned that you might need to check your user profile as well.
So might want to do that.