you might try copying it to another location and then pointing the import export tools addon at the new location and ask it to import mbox files from Users\name\AppData\Roaming\Thunderbird\Profiles\********.default-esr\ImapMail\ and it's subfolders. (whatever you have named the copy.) Make all copies with Thunderbird closed and do the import with it open. https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss

This did not work. I copied the file from Users\name\AppData\Roaming\Thunderbird\Profiles\********.default-esr\ImapMail\ to another location with Thunderbird closed, renamed the file "Charter Email", restarted Thunderbird, pointed to the new file as an import. Now I have a "Local Folder" with a large number of files that don't mean anything to me (addons.json, addonStartup.json, AlternateServices.bin, etc.). 46 files. But no email messages. What should my steps be now? Thanks again for your help.

Let me be clear here is a folder, not a file. It probably does not contain any mail at all But I am prety sure you have imported a load of junk as the files addons.json, addonStartup.json, AlternateServices.bin, etc. are located in the root of your profile ie Users\name\AppData\Roaming\Thunderbird\Profiles\********.default-esr that you have managed to get them into Local folders, I have no idea what you have done/

I linked to the import export tools addon. Did you install it and import the MBOX files from the location as I suggested or did you do something else? It you used the Thunderbird "import" menu I really have no idea what needs to be done to recover from this mess.

Yes, I did as you suggested. First, I made a backup of the directory where the messages are stored. Second, I copied the directory to another location and gave it a different name. Third, I downloaded the Import/Export Addon. Fourth, I deleted all of the extraneous files that somehow got into the Local Folders location. Fifth, I used the Import/Export Addon to Import folders located in the copied directory. I have now recovered into Local Folders quite a few emails that were within folders in that main directory. HOWEVER, there are a number of files that were not in folders but were within the main directory that have not been imported. These files have the extension .msf, such as Inbox.msf and Sent.msf. I haven't been able to import those successfully. Any ideas? Thanks.

For clarification, the folders I successfully imported were (.sbd) folders. I haven't seen any files or folders that are (MBOX). Can you please explain? Thanks again.