Did you use a third-party uninstaller program to uninstall Thunderbird? If not, then uninstalling Thunderbird does not delete your data which is stored in your profile folder. See Profiles - Where Thunderbird stores your messages and other user data

If your old profile folder is still where it should be, you can use the Profile Manager to load the old profile and make it the default. See Profile Manager - Create and remove Thunderbird profiles

No, i didn't use a third party pgm. As I said, i uninstalled thunderbird, thinking it would not delete my data, then installed a newer version downloaded at your site. When this version was launched, I saw that my accounts and data were not recovered automatically. I assumed it was lost, and tried to redefine the accounts. the data may at that point have been deleted. I later found the profile locations, but it was too late - all my years of data were gone. This is of course a disaster for all projects, not to mention financial effects.

I want to say here that i have lost respect for mozilla - that they have produced software that is so potentially disastrous, without any forewarning of dangers, and without making possible restoring old data before demanding new data. I was naive to trust in you, and I am now thinking of changing e-mail client.

Moreover, all this was indirectly caused by the ill-effects of another mozilla product that i had just installed, for vpn. It is because the vpn software was not working properly and additionally was causing other things not to function properly that I ended up with this loss of precious e-mails.

Stans, i will try to follow your instructions as soon as i can and get back to you. Meanwhile, please note that my menus do not exactly resemble yours. See attached image of my present thunderbird. Thanks, Avi PS - i should add that i happened to have a mozbackup of thunderbird dating from 6 May 2021 (unfortunately no more recent), and I have restored that data. Needless to say that leaves me with a blank of 6 months, much of the mail dealing with my current projects and financial dealings; so you can see this is very painful for me (not to mention the enormous losses of time now).

... my menus do not exactly resemble yours.

In the Troubleshooting Information look for 'Profiles' in the left pane, and then click about:profiles in the right column. It's not visible in your screenshot.

i uninstalled thunderbird, thinking it would not delete my data

It doesn't delete your data. Having said that, re-installing the application was completely un-necessary, and you did follow bad advice. Profile files with all your data are stored separately from the Thunderbird program files. The program files are static and do not change (except when you upgrade the Thunderbird application version). Because we store profile and program files separately, you can uninstall Thunderbird without losing your messages and settings, and if something goes wrong with a Thunderbird update your information will still be available. It also means that you don't have to reinstall Thunderbird in order to delete your information or troubleshoot a problem.

Assuming your profile data still exists, follow Stans' suggestion and start Thunderbird with your existing profile. https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-thunderbird-profiles#w_manage-profiles-when-thunderbird-is-open

I later found the profile locations, but it was too late - all my years of data were gone.

If all your profile data is really gone, then that wasn't the result of re-installing Thunderbird.

all this was indirectly caused by the ill-effects of another mozilla product that i had just installed, for vpn.

It may just have been coincidence. Usually the most common cause for problems with Thunderbird files is anti-virus software.

i happened to have a mozbackup of thunderbird dating from 6 May 2021 (unfortunately no more recent)

While I understand that your experience must be frustrating, there is no one else to blame than yourself for not creating backups of important business data on a regular basis.

Note, that MozBackup is unsupported since quite some time, and it may not work properly with recent versions of Thunderbird anymore. Quoting from https://mozbackup.jasnapaka.com/ "MozBackup is not being developed anymore. There are known issues and there is no time on my side to fix all issues and develop new features. Use MozBackup only on your risk. Thanks for understanding."

Backing up a Thunderbird profile is as simple as copying a folder. https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data#w_backing-up-a-profile

Hi Stans and Chris1 - unfortunately I did not find the desired profile in the specified location - it was apparently indeed deleted somehow. My understanding is that it had a distinct file name, and therefore was not written over - yet somehow it has disappeared (it is not in recycle bin). Please, if you have any further suggestion as to where it might have gone, DO let me know. In any case, thank you for your help, which I understand is voluntary. Regards, Avi

If you have manually moved the profile folder to a non-standard location you'd need to look there.

No, Chris, I assure you I did not move it, let alone delete it.

One detail I should add, perhaps, is that before I uninstalled it I had the T-bird BETA, then I installed the regular version (and that's somehow when my profile disappeared). Now I reinstalled the Beta version, but it didn't bring back my lost profile.

Is there perhaps some kind of log of events somewhere that might give us a clue as to what happened on Thursday afternoon about 3.40 p.m. (which is when I downloaded Thunderbird for re-installation)?

The only situation that I can think of that would delete Thunderbird data after or while uninstalling Thunderbird is a third-party uninstaller such as Revo Uninstaller or a "PC optimization" program that's running on autopilot, the likes of CCleaner, Advanced System Care etc. Thunderbird's uninstaller leaves behind the data location untouched, and said programs can monitor your system in the background and detect when you've uninstalled a program and automatically clean up the remnants after you. You can easily end up with such programs on your system as sponsored bundles when installing freeware. I've seen clients using such programs "to keep their systems running fast and clean" and get excited when a pop-up informs them about disk space that has been reclaimed, not knowing what exactly has been deleted from their systems. We may never know if that's what happened in your case, but maybe you can identify the responsible program and perhaps get their respective logs to show exactly what happened. Nonetheless, it's time to review what's running on your system, because Thunderbird's uninstaller simply does not delete Tbird's data. Windows has the ability to keep an audit of operations on files and folders, but this isn't automatically turned on. You have to specifically configure the system to do this beforehand.

Stans, thank you for your kind attention again. I used Windows 10 to uninstall. On the other hand, I do have a program called AVG Tuneup, which maybe did the vile deed (i.e. deleted my Tbird profile). I will write to them and ask them. Do you know how I can find out if my Windows kept an audit of operations? Where in Windows is this switched on or off, and where are results shown? Thanks and best regards, Avi

AVG Tuneup might as well be the culprit, and to make it worse, it could be doing this without any logs for auditing! It "cleans up program leftovers to enjoy more disk space" See https://www.varonis.com/blog/windows-file-system-auditing/ for a detailed article on Filesystem auditing on Windows.

Yes, by elimination it stands as the main suspect.