The master Archive folder has one unread message that won't go away.
I'm running Thunderbird 52.9.1, and I'm viewing my email folders in Unified view.
The "Archives" master folder has three sub-folders, one for each email account I view on Thunderbird. All the messages in all of the subfolders are marked as "Read," and the sub-folders appear in lightface.
The master "Archives" folder name appears in bold, and it has a (1) next to it, indicating that there's an unread message in it.
I don't want to post a screenshot and publicize my email addresses, so here's a replication of what I see:
Archives (1)
emailaddressA
emailaddressB
emailaddressC
How can I get this incorrect "unread message" marker to go away?
Wšykne wótegrona (2)
Select the folder and go to View-Folders-Unread to see if you find the message. Then put it back to View-Folders-All.
If nothing shows up then something is out of sync so do the following... Right click the folder and select Mark Folder Read.
The folder "Archives is in the Unified view. I'd already tried the first suggested remedy, and the second isn't possible; "Mark Folder Read" is not an option on the right-click menu.