I am just wondering if you total folder length may be exceeding Windows 255 character limit on a folder length.

Given that the default location for the mail folder in Windows is already using some 100 of those 255 character. the combined length of all the folder that make the folder structure would not be able to exceed around 150 characters your mentioned folder name is around 50 characters so it's parent folder not only have about 100 characters for themselves to be named in.

A second point is the use of punctuation in folder names. Thunderbird uses the folder name to make a real file in the file system. Using things like :/\| in particular can see strange things happen at the file system level. the / and \ are folder dividers, so telling windows to create Horwood/Bagshaw usually ends up with a folder called Horwood with a sub folder Bagshaw. and then clean up gets messy as well.

so it you can be a little more specific about where you have the folder and what they are called, I am guessing that we can delete them in the file system and make them stay gone. But I do not want to advise you with generic information. This is something you o not want to get wrong.

Thanks very much for your rapid response. I do love to use long, descriptive names and thought you had found the problem here. Unfortunately, that doesn't appear to be the case. The full path names seem to fit under the limit and, AFAIK, I have used no reserved characters.

I've attached a JPEG image of part of the Windows file system view of where the problem(s) lie. Only the items starting with the name "Debbie Barrett" are involved. It appears that Thunderbird creates its own folder struture (.msf ??) at the lowest level but the full path of the longest file name there reaches only 225 characters. The longest folder name at the top reaches 220 but those folders are empty.

The correct items (which function properly) as a Thunderbird folder containing several files are marked in green. The 5 items marked in red at the bottom show as 2 Thunderbird folders since one of the 5 is not matched with an .msf file. These two Thunderbird folders can't be deleted. These are the ones that can be renamed (depending on the order of renaming) and apparently deleted but which mysteriously reappear later. The two Windows folders at the top marked in red are a total mystery to me. They do not appear in Thunderbird. Note that all of the items marked in red have a portion of the end of their names replaced with mysterious suffixes which I did not create. For that matter, I did not create any of these "extra" folders. They were created during drag and drop into the original (correct) Thunderbird folder. I seem to recall some mouse button flutter while dragging one message to that folder but nothing else unusual.

It does appear to me that I should be able to simply delete these rogue files at the Windows level. But I'll wait to hear your verdict as well before proceeding.

Thanks much, Chuck Norcutt

there is something messes up there.

But first a short tutorial.

Folders in Thunderbird are files with no file extension every folder has an index that is used to populate the user interface so it is responsive and a 4Gb file does not need to be read to locate a list of mails. This file has an MSF extension.

So to take your entries in green, they constitute a Thunderbirdv folders.

Now a folder can have a sub folder. In the file system, if this is the case a folder will be created with the extension SBD.

So to fix this

• Delete all the MSF files. On startup Thunderbird will regenerate then. Your data loss will be limited to tags, but very few people use tags anyway.
• Delete the two folders at the top. Unless they contains file. If they do lets have a look at that first.
• Delete the Zero length file. 0kb
• Go to the root of your profile. That is the folder with the default extension. and delete the file foldertree.json.

Startup will be a little slower as the folder pane and the MSF files are all regenerated from actual data. But things should be back to normal (I think)

Thanks again very much. That exactly solved the problem. There was almost no delay in the startup. I'm still very curious about how this happened but it may never be known.