Sounds like you have some software on your computer which can delete temp, session and password files. CCleaner and WiseCleaner are two examples of cleanup software and also some Anti-Virus Products also offer this type of cleanup.

If you like to use those types of product then you need to access whatever program you use and make your Thunderbird profile and all it's subfolder and files exempt from scanning, deleting etc. Typically, thunderbird profile is here: C://User/User Name/Appdata/Roaming/Thunderbird

Douglas, how did you resolve this?

@Toad-Hall

I am not running CCleaner or such software. Not deleting temp.

For me, Thunderbird is on the D: drive. I have used this profile since about 2007/2008. I have used Webroot, Microsoft built-in A/V, and Malwarebytes.

@Wayne Mery

The problem has not been resolved. It just happens.

I have experience with Thunderbird removing passwords from the password manager after a failed connection attempt. The reasons for those are legend in number, everything from simply not being on a network, a saturated connection (thanks kids enjoy the movies) to software making things happen in slow motion.

I think mine go when I cancel on the request for a password box with the save option checked. But I have no experience of it just loosing them. If I check with the dialog open they are there still in the password manager. But unless you are always distrusting of password failures like I am you would not notice. Thunderbird's reaction to a missing password and a failed authentication attempt is exactly the same. It asks you for the password.

BTW do you have any apple devices connecting to the mail account? They can actively prevent connection resulting in a failed authentication attempt.

@Matt,

I am running Thunderbird on Windows 10 with several Android devices (2 phones and a tablet) running K-9. No apple devices. Thunderbird reside on my D: drive on my Lenovo ThinkCentre.

I have 11 email accounts in this setup which originated around 2007 or 2008. I have copied this configuration from Windows XP, Linux, Mac, Windows 7. and finally back to several Windows 10 devices. I have also run it on my laptop (copying the Thunderbird directory back and forth).

I am not sure what happens, but all of a sudden Thunderbird starts asking for passwords after it has been running for a while. I have tried deleted the secmod.db and pkcs11.txt. No rhyme or reason as to when it happens. if I open Settings, Passwords, all of my passwords are gone.

Maybe this is related or not, but when I shut Thunderbird down, there remains a copy of thunderbird.exe in the process queue. I cannot terminate this process with Task Manager, Process Explorer, or the command line TASKKILL /F.

I wish I knew where the passwords are stored and I would copy it back from a backup.

Thanks,

- Doug.

I think password is also my problem when Tbird refuses to open. Message says (and keeps saying) 'authentication failed' and presents an option to 'Retry' or 'Insert new password'. Neither of those work, I get the same answer. This is after I have been using Tbird for more than 30 years without such problems.

Is there any way I can reset my password eg: 'forgot password' or similar? I have version 115.

Nobody seems to know.

If you do not have exactly the same problem then you should have created your own question. You have a Password issue but that is not necessarilly the same as losing saved data which is often due to clean up software deleting required files or a corrupted file or lacking a pkcs11.txt file etc.

i'm not so sure you have the same issue as reported in this question.

EDITED.... This person has created their own question which I've just located.