Is there some trick to bulk Read all those emails without opening each of the 9000+ folders?

Right-click the top folder with unread messages in the folder pane - Mark Folder Read

I migrated all of my 80000+ emails from a previous version of Thunderbird to Supernova.

Not sure what that means. You just need to update the application. There is nothing you need to actively "migrate" in the profile.

Maybe I wasn't clear enough. IN the screenshot you see the folder Player_A-J, and at the time I took the screenshot, there were 4955 unread emails. Now there are 13163 -and counting. You see, Player_A-J is the main folder, and inside that folder are dozens of sub-folders, and inside those sub-folder are the individual folders of dozens of customers. The unread emails are scattered throughout literally thousands of customer folders (approximately 9000). Here's just one example of a partial list of customers with the first name David, and this is just for DavidD-Debra. Right now, the only way to get the messages Read is to right-click and select Mark Folder Read. It could take weeks, if not longer, to do that.

That's why I said "Right-click the top folder". I haven't tried this though.

Sadly, that didn't work. This may give you an idea of the magnitude of the problem is. Here are some screenshots that show how many emails are marked as unread and where they are located. So far I've only found two ways to get the messages marked as read. 1) The easiest way is to select an individual folder then Right-Click and select Mark Fold Read. 2) Left click on the folder, then hit Cont/A and then M.

However, it sure would be nice if there was a way to mark all of the emails in all of my folders as read without having to do it one folder at a time.

BTW, thank you very much for at least trying to help!!!

> I migrated all of my 80000+ emails from a previous version of Thunderbird to Supernova

But there is a step that you did, or set of steps. Please provide all the details.

Before uninstalling the old version of Thunderbird, I copied all of the files in AppData\Roaming\Thunderbird\Profiles (31 gigabytes) to a 4T hard drive. Then after installing the new Thunderbird/Supernova program, I Imported (migrated) all the files (using the Import feature, to the same directory in my C drive. Why did I do it that way, you might ask? My C drive isn't big enough to handle another 32 gigs of data.

I don't know why the read status would have changed for any of these messages.

But I still don't understand why you felt the need to copy off your data - and you shouldn't need to uninstall the old version. If you had simply let Thunderbird update on it's own, it would use your original profile data.

When you right click on the account, you can choose "mark all folders read".