To fix corruption in those files you delete them not copy them that can be worse than where you started. The passwords are encrypted and the key is profile specific

However you have said a vast amount and said essentially nothing useful for anyone to advise you. You are looking at the registry. Thunderbird really does not use it, except for some windows system integration things like the default mail program newsreader etc. It stores no account information connection setting or password in the registry, nor does it use the windows certificate store. As many third party antivirus products use self signed (and untrusted) certificates that they programmatically add to the Windows certificate store but can not add to Thunderbird. They have issues blocking the reception of mail as Thunderbird does not trust the connection as the certificate used is not trusted. These errors often bubble up as incorrect password errors. Just about any connectivity issue, especially those caused by security software, appear as a password input request. So you might not be looking for corruption at all. Have you checked to see if a password appear in the password manager?

I have also seen a lot of issues in recent years caused by the use of VPN software. Most mail providers will have issues with it's use when getting mail. Especially if the same account is accessed from apparently different part of the world in short time-frame as might be expected when a local phone and an international VPN location both get mail from the same account.

I have nothing nice to say about the continued production use of windows 7. I still have some offline devices running windows98. But they will never see a network, let alone the internet. Therefore I do not need security software on them either so they function as designed in accessing satellites etc. There have been to many critical security issues since V115 was released for me to suggest anyone is safe enough to use it day to day, https://www.mozilla.org/en-US/security/known-vulnerabilities/thunderbird/#thunderbird140

Thank you, Matt 1) I found and solved the problem. Several years ago I had loaded TB on this computer, but was unhappy with it. I uninstalled it. But, at the time I did not realize I had to also delete the folders. Spiceworks suggested using %appdata% and %localappdata% to locate the folders. I did this and deleted them. The folders had the old profile information that was no longer valid. Spiceworks also listed a number of registry keys to check...they were all empty. After deleting the folders, I re-installed TB without difficulty. Lesson learned. 2) I have been programming since 1966 (beginning with mainframe Fortran!!). I still have computers with Win98SE, Win2000, and XP as well as Win 7, 10,11. I even have my old MS-DOS diskettes, but they are in a box in a closet. Why? Two reasons: I was an engineering professor for over 35 years, during which time I wrote hundreds of PC programs in Fortran, Basic, and QBasic. I still write an occasional QBasic program. None (including executables) will run on 64-bit 7, 10 and 11 computers. Some of the programs I can import into Excel VB, but there are too many limitations, especially in formatted output. Of course I keep the old computers off the internet. Second: Although long retired from academia, I still do a little consulting now and then. I have some very expensive printers (dating back to the early 2000's) for which there are no drivers for 10 and 11, and a scanner for which the last drivers were XP. At this point in life it is (as Spock said) "not logical" to invest in a lot of new hardware, although I bought a several inexpensive Brother monochrome printers for which there are 7,10,11 drivers, and new HP color laser printer for which the drivers were only 10 and 11. The old and new printers are on my home network, and I print to each from the corresponding computer.

Anyway, thanks for the reply.

I am shifting over to TB from Windows Live Mail. I have installed TB Ver 115.16.2 on 7 computers successfully (Win 7, 10 and 11) over the past year. But on one Win 7 computer TB will not save the password. Usually TB asks for the Password during set-up. But here it asked for it in a pop-up box. Yes, I entered the correct password. Yes, I said "save with Password manager." But here it keeps asking for it, over and over. At one point TB connected to the POP download server, just long enough to download all the incoming emails, but then quit connecting. It won't connect to the SMTP server. The port numbers for POP and SMTP are correct and the security settings are correct. I've done a lot of web searching. Most sites say that profile files logins.json and key4.db may be corrupted. I disabled them (by renaming) and copied those two files from another computer on which the same Thunderbird version works properly on the same mail server. Same thing - TB still keeps asking for the POP server password. I just deleted TB (uninstalled, and deleted all the appdata directories, and verified there were no lingering registry keys using a list shown on Spiceworks). I'll next reinstall, but don't have much confidence that it will work. Thanks.

Sounds like a **profile or Windows credential issue**, not just Thunderbird itself—especially since reinstall didn’t help.

On that Win 7 PC, try creating a completely new Thunderbird profile and also clear any saved entries in Windows Credential Manager, that usually fixes the endless password prompt 👍