Thunderbird stores it's mail in MBOX files, but they have no file extension. So try using the import export tools to import mbox files. https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss

Thank you, Matt. I have tired to import this addon many times and I get this message:

Unable to install add-ons (extensions or themes) in Thunderbird Beginning with Thunderbird version 60, add-ons that have not been updated by their authors may stop working. Likewise, in Thunderbird beta version 63, add-ons that have not been updated for the beta by their authors may stop working.

An inability to install an extension can be the result of problems with the extension or the version of Thunderbird you are using. This article describes various causes of install problems and what you can do to address them.

P.S. I am using Thunderbird version 68.7.0

have you gone to the addon manager in Thunderbird and searched for the import tool. Then picked the one that works with Thunderbird 60-68. Namely the one with the NG on the end of it's name, the same one I linked to. (BTW the NG stands for new Guy as the original author abandoned the tool. So you will see importexport tools and import export tools NG both listed in most searches. You want the NG version.

The old Inbox, or any other folder, can be copied from the backup profile to the active profile by copying the Inbox mbox file - the large file named Inbox, with no extension, in Mail/<popservername> or ImapMail/<imapservername> in the backup profile - to the Mail/Local Folders location of the active profile. Do this with TB closed. When TB is restarted, the backup Inbox should appear under Local Folders in the Folder Pane. Help/Troubleshooting, click Open Folder to open the active profile folder in File Explorer.

Thank you both very much! I imported the NG (had not chosen the right one previously) and also had to import the import/export app. I had neither program on my Thunderbird. NOW I will try to move my emails back to the inbox.

I am still unable to move the deleted inbox back to TB. I go to Tools>ImportExportToolsNG>Import M Box file> choose "Import Directly One or More M Box files." Click OK. Then I select "Mail" and click open. All that appears in TB is "mail" with numbers following, without the deleted emails. What am I doing wrong? I feel really dense. Any help is appreciated.

What is "Mail"? Select Local Folders, then Tools.....Import mbox file, in the 'Select the mbox file to import' window, the folder displayed at the top should be the profile folder, which looks like:

C:\Users\username\AppData\Roaming\Thunderbird\Profiles\8characters.default

For POP accounts, open the Mail folder, ImapMail for IMAP accounts, then open the subfolder for the removed account, e.g. pop.gmail.com or inbound.att.net or imap.mail.yahoo.com. Then, you will see a list of the mbox files and .msf files (see picture). Select the one with no extension, e.g. Inbox.

To recover a few folders, it's probably easier to just do it manually as already described above.

This is a screenshot of my choices. I am totally confused.

Your picture shows you've selected the Inbox mbox in pop.centurylink-1.net. Look also in the New Inbox backup and New Inbox backup.sbd folders, and then go back to the Mail folder and see if there is a pop.centurylink.net subfolder of Mail (not Mail/mail backup). In future, don't store your backups in the profile folder.

Thank you. I will try your suggestions.

Again, thank you for your help. I have made so many attempts to recover my old emails that I now have multiple inbox folders that I cannot delete no matter what I try (see attached). I give up! You have been very generous with your time and expertise. Thank you.

I think the best option is to create a new profile, from Help/Troubleshooting, about:profiles, and add your account. Then, if you decide to import mail from the old profile, import it to Local Folders only, using the instructions provided in this topic.

Finally! Thanks to your guidance I have restored my deleted emails back to TB. Couldn't have done it without you.

Now that all the deleted emails have been restored to TB, I have folders that will not delete. I would like to delete the "New Inbox Backup" and its sub folder, but nothing I try works. Any ideas would be appreciated.

A screenshot of the inbox that will not delete.

Open the profile folder, close TB, open the subfolder of Mail that contains your account and post a picture of the file structure. In future, do not store backups under the mail account - put them under Local Folders only - and don't restore existing backups to a position under the mail account..

Sfhowes, thank you for responding, again.

The "new inbox backup" and its sub-folder are empty. I didn't save them there. Hope this is the correct screenshot.

Here is another file structure view.

What's inside Inbox.sbd? I would expect there's a New Inbox backup mbox and .msf, and new Inbox backup.sbd, which contains another Inbox mbox and Inbox.msf.

If you're worried about deleting things that are empty anyways, just leave them, or move them outside of the profile folder and restart TB to see if they have disappeared.