Safe mode applies a number of features besides disabling add-ons. The most common are a default layout ('Reset toolbars & controls' to fix) and disabled hardware acceleration (under Preferences/General/Indexing). I would guess that the layout is broken, and the password checkbox is not being read. This probably was a result of re-using a profile used in an older version of TB, which itself was based on a Eudora conversion. Launch in safe mode, 'Reset toolbars & controls', 'Make changes & restart', and see if that fixes it.

Thx for your reply. I restarted in safe mode, in the dialogbox that pops up I checked "Reset toolbars & Controls" and chose "Make changes and restart". Unfortunately, apart from the windows being resized, this made no changes to the behaviour. It's peculiar: When I enter the mail password and leave the "save pw" unchecked, all is well and my mail is fetched. When I do check the "save pw" however, the status bar says "Connected to ..<provider>" but my mail is *not* retrieved from the server and the pw is not saved. In save mode, the password is remembered correctly and file "logins.json" is created/used in the profile folder. I am not familiar with Thunderbird (yet) - is there a clean settings- of preferences-file that I could copy from the default profile, without losing all my folders and addressbook-entries?

Who is the mail provider, and what are your authentication method settings?

The best way to start with a clean slate is to create a new profile, add an account, and test the password performance. Help/More Troubleshooting, about:profiles, to create and launch profiles. Your current profile is unaffected and can be launched as before. If the new profile works properly, data can be transferred from the other profile.

Mail provider is Ziggo.nl. Incoming server pop.ziggo.nl, TLS/SSL, port 995. I created a new profile a few times, swapped between POP and IMAP but it doesn't really help. In safe mode, Preferences>Saved_passwords shows a few lines of saved login info. In normal mode, this list is empty. Also, an attempt to create a master password fails with a non-explanatory message. Looks like TB has problems reading/writing the password/logins-file in normal mode, but why?

If you have a security app, e.g. Avast, Kaspersky, that includes a password manager, that could interfere with TB saving passwords. If the manager were injected via an extension or plugin, that would explain why there's no problem in safe mode.

I have no securitiy app whatsoever. Running TaskManager, I noticed that running TB in normal mode I have 2 TB-processes active, while it appears that when running in safe mode I have only one. Does that make sense?

I turned on the Error Console and noticed errors like "NS_ERROR_FAILURE: Couldn't decrypt string". Looking for that message in the forum I found an advise to delete files cert8.db, cert9.db, key3.db, key4.db, logins.json and secmod.db. That solved my problem. Thanks very much for your assistance. Gert Huber

I have 2 TB processes active, so I don't think it matters as far as your problem.

Deleting the .db files is a standard remedy for password issues, since TB recreates them on restart. But since you tried a new profile, with default, empty db files, and the problem remained, I didn't suggest that remedy.

In current TB, the relevant files are key4.db, cert9.db, logins.json and pkcs11.txt; the others are obsolete.

Thank you very much for solution. Got the same problem with 96.03 (Windows 10 x64). After deleting cert*.db, key*.db, logins.json and secmod.db in profile "Save passwords" works.