delete the file foldertree.json from your profile folder with Thunderbird closed.

Thanks Matt. But this did not solve my problem. Here are the steps I followed: 1. Last night: closed all my applications (including Thunderbird) then shutdown my computer. 2. This morning: Powered up my computer; the startup process automatically opens Thunderbird. 3. I checked this email folder again. There were two of these folders again (same name), and both were empty. 4. I closed Thunderbird and deleted file "C:\Users\Sam\AppData\Roaming\Thunderbird\Profiles\ardwce2w.default-esr\folderTree.json", then restarted Thunderbird. 5. The problem folder was still there (two instances) and both were empty. 6. File folderTree.json had been recreated, but a bit smaller than before. 7. I repeated step 4, but there was no change in the results. In fact, I repeated it a couple times, with no change in the results.

First item is remove Thunderbird from the startup group. Despite folk thinking it is a good idea, it is a poor choice to have Thunderbird start while the operating system does so. It can, and has in the past, caused issues only seen when Thunderbird starts in that manner based on timing of other programs starting and services becoming available. Windows offer you the desktop before it actually is fully loaded, so starting programs in a partially loaded operating system can be problematical. So take it out of there for diagnostics at least.

Next we have files which apparently have numbers after them. While I am not familiar with this as such It could be Thunderbird escaping the path as it contains an underscore. But when trying to find something on google, I see a lot of folks seeing number following file names where the folder is redirected to Microsoft's cloud drive. Apparently this can happen, but It is new to me as I don't use cloud storage any more than I have to. But having startup complete before Thunderbird starts might stop that.

Copy the file Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker to C:\Users\Sam\AppData\Roaming\Thunderbird\Profiles\ardwce2w.default-esr\Mail\Local Folders and rename is a baker, then paste it again with the original name. Start Thunderbird

Did local folders get two new folders, both with mail in them?

The idea of renaming the file to baker is to determine if there is something in the extensive punctuation and special characters that is the problem.

It will also, by leaving the name unchanged, check my belief that your path to the files is actually the issue

The string C:\Users\Sam\AppData\Roaming\Thunderbird\Profiles\ardwce2w.default-esr\Mail\Local Folders\MailStore Export.sbd\Outlook gmail.sbd\Organizations.sbd\_Service Providers.sbd\Health Providers.sbd\Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker is 253 characters long. The upper limit for windows path is 256 characters. My guess is Thunderbird adding File:// to the start of the path per UNC conventions will see the file not being read correctly because it is just to far from the root of C:

Hi Matt, This helped to solve the problem. Thanks a lot. I tried two or three different things, what eventually worked was changing the long file names in Windows Explorer to a short file name, then restarting Thunderbird. After this, all emails are now visible in the folder with the shorter name.

In more detail, here are the steps I tried and what was eventually successful: 1. Within Thunderbird: - renamed folder from "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker" to "Cleveland Clinic - Shelagh Baker" - deleted second folder named "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker" 2. Closed Thunderbird, then opened again. No change. Still no emails visible in folder. - second folder named "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker" likely recreated, which I deleted 3. Within Thunderbird: renamed folder from "Cleveland Clinic - Shelagh Baker" to "baker" 4. Closed Thunderbird, then opened again. No change. Still no emails visible in folder. 5. Within Windows Explorer, directory "C:\Users\Sam\AppData\Roaming\Thunderbird\Profiles\ardwce2w.default-esr\Mail\Local Folders\MailStore Export.sbd\Outlook gmail.sbd\Organizations.sbd\_Service Providers.sbd\Health Providers.sbd" - two empty sub-folders exist named baker and "Cleveland Clinic (Sports Medicine Specialists) 0554d8b9" - file baker.msf exists - file "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker" exists - file baker does NOT exist - I deleted the folder named baker - I renamed file "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker" to baker 6. Start Thunderbird. Folder baker within Thunderbird now contains all the emails. 7. Within Thunderbird: - renamed folder baker to "Cleveland Clinic - Shelagh Baker" - deleted folder "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker" 8. Closed Thunderbird. 9. Within Windows Explorer, directory "C:\Users\Sam\AppData\Roaming\Thunderbird\Profiles\ardwce2w.default-esr\Mail\Local Folders\MailStore Export.sbd\Outlook gmail.sbd\Organizations.sbd\_Service Providers.sbd\Health Providers.sbd" - confirmed files exist named "Cleveland Clinic - Shelagh Baker" and "Cleveland Clinic - Shelagh Baker.msf" - had planned to manually delete any file or empty folder named "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker"; but unexpectedly, found there were no such files or folders 10. Start Thunderbird. Within Thunderbird confirmed: - folder "Cleveland Clinic - Shelagh Baker" exists with all the emails - there is no folder named "Cleveland Clinic (Sports Medicine Specialists) - Shelagh Baker"

Thanks again for your explanations and assistance in fixing this problem. It looks like you are correct re: the length of the file name was the root cause behind my issue.