how about a screen capture showing the folder. It's icon etc are crucial to trying to understand the issues that may be causing this. Everything from a bad antivirus to incorrect settings in Thunderbird could be in play.

Sure... Here ya go....

The highlighted line is the ever-recurring zombie folder. If deleted, it does not appear again until restarting TB. The b571e9o8 ending of the folder name was appended to the name by TB during the original deletion process. It was not a part of the original folder name. This exact situation has happened dozens of times now and is consistent.

That garbage at the end makes me think you may have hit the windows limit for describing a file

go to the account settings and on the server settings page there is a local directory setting. What is it? (note highlighting with your mouse and pressing Ctrl+C will copy the value so you can paste it later.)

now in the troublesome folder, right click it and select properties.

again what is the location? It will start with mailbox:/// the the account directory should form a part of the location, but this time the whole string it the important thing. (the same Ctrl+C with a mouse will work here to copy) What is the size on disk?

Windows is weird, it lets you create paths more than 256 characters, it even displays them, but it will sometimes not let you delete them.

It may be all that is required is to use windows file manager to force the delete and Thunderbird can catch up next time it starts. To that end, close Thunderbird and open the file explorer.

using the location you determined from properties navigate to the appropriate location. (using %appdata% in the location bar and pressing enter will take you to the normally hidden appdata folder where profile are usually stored.) Look for both files with the name of the folder and a sub folder with an SDB extension in the pending and orders folder.

A folder as shown in the user interface of Thunderbird is represented in the file system as two files. One without an extension (the mail in the folder) and an MSF file, the most file being the index of mail in the other file and a sufficient summary of the mail to populate the user interface. If the folder has a sub folder in the user interface, it is shown in the file system as a folder with the same name as the files, but it has an SDB extension.

Just delete anything starting with the 20241122 I think is probably safe on this occasion. Click to go up two levels in the file explorer locate the folder tree.json file and delete that.

Restart Thunderbird and I think all will be good.

Hi Matt..... Thanks for jogging my gray matter. I finally dug way deep enough into the profiles / local folders, etc., to find this folder lurking with zero bytes. I deleted it there and then deleted it from the trash/recycle bin on that drive. (I have 6 ssd's). It has not come back (yet)  :^). Thanks again!