I cannot add my outlook account to Thunderbird

Hi Jeff Black,

Welcome to Microsoft Q&A forum. 

From the message shown, this does not appear to be only a password issue. Outlook.com/Hotmail accounts now require Modern Authentication/OAuth2 when used with third-party mail apps such as Thunderbird, so the account should not be configured with “Normal password” authentication.

Please try the following steps:

1. Update Thunderbird to the latest version, then restart Thunderbird.
2. In Thunderbird, go to Settings > General and check if any experimental Account Hub/setup option is enabled. If it is, turn it off and try adding the account again.
3. Add the account again and choose Manual Configuration if available.
4. Use these settings:
   • Incoming server: outlook.office365.com
   • Port: 993
   • Security: SSL/TLS
   • Authentication method: OAuth2
   • Outgoing server: smtp-mail.outlook.com
   • Port: 587
   • Security: STARTTLS
   • Authentication method: OAuth2
   • Username: your full Outlook email address
5. Also make sure IMAP is enabled in Outlook.com by going to Settings > Mail > Forwarding and IMAP, then turning on the option to let devices and apps use IMAP.
6. If Microsoft shows a recent IMAP sign-in attempt, please confirm it was you from the Microsoft account Recent activity page, then try adding the account again.

If the same “Unable to connect to localhost” message still appears, the issue may be with Thunderbird’s OAuth sign-in window or local callback process. Since Thunderbird is a third-party app, I recommend also checking with the Thunderbird Help Community for more specific troubleshooting on that localhost connection screen.

Please feel free to let me know if you have any further updates, thanks.

Since this is a public forum, we will hide your personal identifiable information, and I have sent that image of yours containing your personal identifiable information in a private message so we can work together to resolve the issue. Also, please check your private message in case you want to share another screenshot to avoid leaking your PII by click on the Private Message button as show below

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".  

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.