It 'sounds like' you installed Thunderbird from Microsoft, not the official site at thunderbird.net, in which case your profile is probably at AppData\Local\Packages\MozillaThunderbird If so, my personal recommendation is this:

- locate the profile, preferably a thunderbird\profiles<profilename> structure similar to regular thunderbird - copy to safe location while thunderbird is NOT running - uninstall thunderbird and then download and install from thunderbird.net - copy the saved thunderbird folder to the place you are already aware of as default - restart thunderbird

I omitted little details on exact file placement as you seem familiar with that. There is nothing wrong with the Microsoft version, but if you ever need to do troubleshooting, that feature doesn't work. NOTE: when going to thunderbird.net, the default is the monthly version. if you want the ESR version, you must select it from the options.

Thanks for the answer! I can now do the backups with the folder you gave me - no real need to re-install Thunderbird.

Thanks for the answer! I can now do the backups with the folder you gave me - no real need to re-install Thunderbird.

Except the peculiarities that accompany the version you have installed and it's "sandbox" are not well understood by the folks that inhabit these forums. So you support experience will probably not be very good. Can Thunderbird even find it's profile. Go to Troubleshooting information on the help menu and click the show profile button. Can Thunderbird locate it's own profile here? It could not a while back and it is simply one issue.

jmm, thanks for the feedback.

Can you suggest wording changes/additions for https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile ??