have you checked the setting? I have not updated yet, so that it has not happened to me is not relevant. I will update now and see if I am also afflicted.

Performed the update and I am seeing no new mozmsg or mozeml fles.

What drew your attention to these new folders?

I use to keep a copy of my local folders in a USB memory stick using a synchronization program (Easy2Sync for Files), which allows me to have access to all messages from my laptop and office as well. It's convenient and takes only a couple of minutes. I ave been doing so for years. But now the synchronization program finds dozens of new *.mozmsgs folders, which makes synchronization practically impossible. I can't really imagine what might have caused the problem.

I have installed the following add-ons: G-Hub Pro, Manually Sort Folders, Signature Switch, and Xpunge. I thought that Manually Sort Folders might be an issue (as it is not fully compatible with the latest version of Thunderbird) and deactivated it but the *.mozmsgs started appearing again after a while.

As I mentioned in my first post, I have double-checked to make sure that the Windows integrated search option is deactivated. I would appreciate any ideas...

run Thunderbird i safe mode (help menu > restart with addons disabled and continue to safe mode when prompted. Sill seeing them created?

I'll try safe mode for a while to see what happens and will let you know. If everything works smoothly, I suppose the problem can be attributed to an add-on? Would it then make sense to start introducing add-ons one-by-one to see when the *.mozmsgs folders appear again?

Many thanks for responding to my request!

if things go well in safe mode, just restart and see if they go bad again. I have seen simply using safe mode fix issues permanently and I have no idea why. But it is not the expected behavior.

Unfortunately, safe mode did not help at all... *.mozmsgs folders keep reappearing with absolutely no reason shortly after I start Thunderbird. I am also posting a picture showing what I mean. It's crazy... I have been spending valuable working time on this rubbish...

Well, I installed Thunderbird 72 beta 3 to see if the problem is fixed. But then no add-on would work. So, I decided to revert back to Thunderbird 60.9, as a version that was fully functional on my computer. But as long as I installed it, it automatically updated to version 68.4.1, which is exactly the one I already had in the first place! Now, I have been using it for a while and it seems to be working properly, i.e., no unwanted *.mozmsgs auto-generated. I come to think that there was probably a bug in the Greek version of Thunderbird 68.4.1 that I used because the English version works fine. If the problem persists, I will post an update. Again, many thanks for your time and recommendations!

You might also check the hidden preference mail.winsearch.enable in the config editor. This is the setting the user interface button changes. Just in case there is a disconnect between the two in your case.

Well, I don't know if this setting was true when I had the problem, but now it is set to false and everything works fine. I'll keep that in mind if I come up to the problem again in the future. Thanks for the prompt support!