Can you post a screenshot of the backed up profile? Was it created with the Thunderbird export feature?

The following article should help you figure where to look for your profile data. If you can find the profile folder associated with the profile you were using somewhere, then you may restore your mail, because all your mail data was being stored there:

https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data

If that profile folder was stored in an enclosing Profiles folder within a Thunderbird folder, then restoring the whole Thunderbird folder would make things much easier because then you would also restore the profiles.ini file that Thunderbird uses to keep track of your profiles.

If you only have a profile folder that was stored in a non-standard location outside the Thunderbird folder, then you can still restore it, but you'll have to tell Thunderbird where your profile data is by either reusing an existing profile or creating a new profile and make it use the profile folder you have:

https://support.mozilla.org/kb/profile-manager-create-and-remove-thunderbird-profiles

Hello David, please excuse my poor English. But I hope that the online translation help will do its job.

I don't think that it was created with the Thunderbird export feature. The data backup always took place (after confirmation) when Thunderbird was closed. It could be that an addon was installed. Unfortunately, I don't know which addon.

Greetings from Germany Rüdiger

Try this, assuming thunderbird is already installed - exit thunderbird if running - copy and paste the profile folder to c:\users\<yourid>\appdata\roaming\thunderbird\profiles - start thunderbird and click help>troubleshootinginformation - scroll down to 'profiles' and click 'about:profiles' - now, click the 'create profile' button - click next - enter a short name for the profile, such as MYPROFILE -now, click the choose button and locate and select the profile you copied in - click finish and launch If the profile was complete, thunderbird should start. If, instead, you're prompted to create an email account, that indicates the profile has a problem, and the contents may need to be manually copied. Let us know.

Hello David GG

Thank you very much for pointing out the links with the very helpful explanations. This helped me a lot to get a basic understanding of the file structures of Thunderbird. With the subsequent instructions from David, I finally managed to restore my messages. I am very happy - thank you again. Greetings from Germany Rüdiger

Hello David

Thank you very much for your really good instructions. I actually managed to finally restore my messages with it. I am very happy - thank you again.

Greetings from Germany Rüdiger