I just upgraded my desktop pc from Windows 10 to 11, and before the upgrade I used the Tools Export function to export my complete Thunderbird profile, so I could import it after the upgrade. Unfortunately the export file cannot be read on my upgraded pc using the Import function - Thunderbird gives me error messages every time, that suggest the exported folder might be corrupted or invalid. My IMAP emails are fine, as I have set those accounts up from scratch and the folders have now populated with all the emails - the problem is all my filed emails, dating back many years, which were all stored manually in a filing system under Local Folders. I tried manually copying across the individual files from the extracted back-up folder into my live Thunderbird profile and then reopened Thunderbird...which worked to some extent...as in, all the folders are there, but no emails are showing! It shows no messages under each folder, even though if you look under the Profile you can see that the email files exist. I tried various ways to bring them in, including zipping one of the folders and trying to import from the zip file (which also brought in a folder but no emails) but even though the email files are clearly there under my profile, Thunderbird shows 0 messages in all my Local Folders. It's as though it is unaware the files exist, so I suspect it needs them to be formally imported somehow? I would hate to lose the emails, as they document important information and purchases etc over many years, along with archived emails for my charity work, social events, etc. As I said, I can see the files are there but simply copying the files to my profile has only worked to the extent the filing 'structure' is visible, Thunderbird doesn't display any of the emails. I have included two images...one of my Thunderbird Local Folders as they currently look, and the other showing the backed up files existing in my Profile, which I hope are helpful. Can anyone help please? I am running a desktop PC on Windows 11. Thanks, David.