Every time I open Thunderbird, old folders appear with a bunch of gibberish. Even when I delete them, they keep returning every time I reopen Thunderbird. How do I delete them for good so they don't keep reappearing? They don't harm the function of Thunderbird, but it's just annoying to keep having to delete them.

I've attached a screenshot to show what I'm taking about. If I close Thunderbird without deleting these folders, the next time I open Thunderbird, there will be 3 of these folders. Close again without deleting...I'll have 4 the next time I open it. Etc...