Because imap account folders constantly synchronise with server folders to show what is on server, you have to assume they are also stored on server even if you downloaded full copies. Usually, you synchronise all folders for offline use to download full copies and move emails out of imap account into Local Folders account before closing the account. Assuming you have got copies of fully downloaded emails in that imap account. Check to see what is stored. In Thunderbird Help > Troubleshooting Information click on 'Open Folder' A new window opens showing contents of your 'profile name' folder. click on 'ImapMail' folder click on the imap mail account name folder Downloaded Emails are stored in mbox files; mbox files do not have any extension. (These are files you would need to get imported into Local Folders mail account.) You should see *.msf files ; they do not contain emails; they are just indexing files. If you see *.sbd folders, this means you created subfolders, so the *.sbd folder might contain mbox files and *.msf files. In Thunderbird. Try to use the following to get copies of mbox files into your 'Local Folders' mail account. Install addon 'ImportExportTools. * https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools/ how to install addon: * https://support.mozilla.org/en-US/kb/installing-addon-thunderbird Restart after installing. Right click on 'Local Folders' mail account in Folder Pane and use 'ImportExportTools' > 'Import mbox file' Choose first option to just import mbox file. Choose second option if importing an mbox file that had subfolders. click on OK window opens allowing to locate mbox files. Locate the mbox files in your profile name folder which you viewed earlier and click on 'Open' to import into 'Local Folders' mail account. Repeat as necessary.

That helped! Thank you!