Try the following: • go to Settings > General > scroll to the bottom line and click the "Config Editor...." button • search for the preference mailnews.oauth.usePrivateBrowser and toggle its value from false to true • restart Thunderbird

Dieter did you have good results?

It is always the same problem. I have no access to yahoo about thunderbird. With other email programs, like Microsoft Outlook, i have no problems. Also on my smartphone and tablet i have acces to yahoo. In Thunderbird i became always the answer: Something is going wrong!

The reason you are unable to login to your account, is Thunderbird version 148.0 has a code change to meet new OAuth2 authentication requirements from Yahoo, ATT and AOL, a new protocol called PKCE. This requires you to reauthenticate (login) to your account, even though the authentication method remains OAuth2.

The other programs might not have made this change, or might not have authentication set to oauth2.

Below are a series of steps to narrow down your issue... (we are skipping section A)

B. Please tell us:

B1. With the password that failed with Thunderbird, can you log into the account(s) using the mail provider’s web interface (webmail)? (Note: you must use the account password, not an “app password” that was created by yahoo) B2. What are the full domain name(s) of all the affected account(s) - the part of your email to the right of the "@"? (for example yahoo.co.uk) B3. Are cookies enabled in Thunderbird at Settings > Privacy & Security > “Accept cookies from sites …” ? B4. Are you able to login using Thunderbird after you do the following

• Settings
• Config Editor
• Click 'Accept the risk and continue' if that appears
• Find mailnews.oauth.usePrivateBrowser (screen shot below - you can paste it into the search field)
• Click the two-headed arrow icon to toggle false to true

* Restart Thunderbird (make sure it has fully shut down before starting it up)

• Retry the login

C. If you were not successful after B4…

C1. Can you see the entire oauth dialog panel - no action buttons are missing? C2. No authentication dialogs are hidden behind what you currently see? C3. You don’t have the preference javascript.enabled set to false in Settings > Config editor? C4. Are you in the country in which you normally use the account? (rule out geoip) C5. (related to #4 above) Are you using a VPN? C6. Is the authentication method in Account Settings set to oauth? C7. Are you using MFA/2FA? (enabling multi-factor authentication / two-factor authentication in your mail provider settings might be blocking you) C8. Are you running a webserver on your computer? Or is any program listening on port 80 [1]? (skip to next step if you don't know) C9. If you are using Windows, does it help to start Windows in Safe Mode with networking enabled? See https://support.microsoft.com/en-us/windows/windows-startup-settings-1af6ec8c-4d4a-4b23-adb7-e76eef0b847f. If you feel the instructions are too complicated, printing them often helps.

[1] check for program listening on port 80:

• macOS and Linux, a terminal window - sudo netstat -an | grep LISTEN | grep :80\D
• Windows, in a command/dos window - netstat -an | findstr LISTEN | findstr ":80[^0-9]"

If you are really stuck, sending us screen shots might help. (Attached are some screen shots of what a user of yahoo should see.)

Ich habe alles ausprobiert, aber es funktioniert nicht. Siehe Bilder

In den Einstellungen habe ich alles probiert und geändert, aber es geht nicht.