I add that while I can setup account, Thunderbird refuses my password, although it works previously under Windows 10 (just before the upgrade) and works another computer running under windows 10 too. It seems that the last release of Thunderbird is not compatible with Windows 11... How to solve this issue ?

You might consider making some information available so your assertions and false ideas can be tested. I know Thunderbird works with windows 11 as I have been using it in Windows 11 for years. What I do not touch is portable apps.

Firstly, Outlook uses oAuth authentication exclusively, so your password is not relevant at any time after the initial authorization. Generally folk having issue have meddled with the cookies setting in Thunderbird. they are permitted by default. Or they have installed software like Apache server or a mail or development tools that monitor and consumes packets received on the loopback address of 127.0.1.1

If your "specific national operator"- is ATT they also do not use your password except in their case it is at all. You have to use something they call a secure mail key instead of your password. Others like AOL, Yahoo and Gmail all use oAuth as does Outlook.

So how about I stop guessing and you explain exactly what the issues are with exactly what mail providers.

For my national operator, when I try to setup the account email, the test works but then I get the next error when encoding the existing password (under Windows 11, Thunderbird 142.0 64 bits):

Erreur d’authentification. Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIMsgAccountManager.createIncomingServer]

Do you have the same Thunderbird version on both Windows 10 and Windows 11 ?

The portable used TB v142 under Windows 10 without issues. I simply upgraded to Windows 11 when the OS asked me for. All aplications work properly but TB. As I cannot setup any account, I deleted TB, then reinstall it, but the issue remains.

At last resolved ! For the first email address to an external operator (P&T), in fact the password was incorrect (and I was not connected to the webmail service in parallel, what could also be a source of error). For the second email address (Outlook one), my mailbox was open in parallel on the webmail service via Outlook.live. It seems that in this case, when trying to create the same account (email address) in Thunderbird, the application is unable to validate the password, even if it correct. Thus I had to close my Outlook.live session in order to set up my account in Thunderbird.