Problem with getting outgoing email server to work in thunderbird

Question

I am new user of outlook with basic outlook account with elevated storage area. I am using outlook in Thunderbird. I can receive incoming emails but cannot send emails. Sever settings seem to be correct. Have re entered outgoing settings many times. when trying to send a message, an error comes back "Login to server smtp-mail.outlook.com with username ******@outlook.com failed." with 3 choices for input boxes : " Retry; EnterNewPassword; Cancel"; Retry doesn't help; cancel --cancels; Enter New Password -- When selecting it, it seems to jump to my browser, which is Firefox, but doesn't open a tab or display anything. How to fix this please. I saw a little info that new outlook accounts have the outgoing server blocked for a period of time. Don't know if this is true. If it is, please remove the block Thanks and regards.

Answer 1

For Outlook.com in Thunderbird, the most likely cause is that the account is still using basic authentication or the OAuth sign-in flow is not completing for SMTP. Outlook.com requires modern authentication for third-party mail apps such as Thunderbird.

Try this in Thunderbird:

1. Open ≡ > Account Settings.
2. Select Server Settings for the Outlook.com account.
3. Set Authentication method to OAuth2 instead of Normal password.
4. In the left pane, select Outgoing Server (SMTP).
5. Select the Outlook.com SMTP entry, then choose Edit....
6. Set Authentication method to OAuth2 instead of Normal password.
7. Save the changes with OK.

If it still fails, remove the Outlook.com account from Thunderbird and add it again. Re-adding the account lets Thunderbird detect the proper modern authentication settings automatically.

If Thunderbird shows a password prompt or the browser handoff does not complete, that matches the documented Outlook.com issue with non-Microsoft mail apps that must switch from basic authentication to modern authentication.

If the SMTP settings are not being detected correctly, get the SMTP settings from the mail provider and try the advanced/manual setup again.

No supported information indicates that new Outlook.com accounts have an SMTP sending block that can be removed through this channel.

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• Outlook and other apps are unable to connect to Outlook.com when using Basic authentication | Microsoft Support
• Modern Authentication Methods now needed to continue syncing Outlook Email in non-Microsoft email apps | Microsoft Support
• Error: SMTP Autodiscover Failed | Microsoft Support