Outlook Login Problems

Fix Thunderbird Hotmail OAuth2 Authentication Errors

Aamir Naveed Akram Sep 28, 2026 869 views

Question details

The user needs to resolve repeated password prompts and authentication failures when connecting Hotmail or Outlook.com accounts to the Thunderbird mail client via OAuth2.

How to Fix Thunderbird Hotmail OAuth2 Authentication Errors

Product: Thunderbird and Microsoft Outlook.com
Device & OS: not provided
Scenario: Connecting and authenticating a Hotmail or Outlook.com email account within the Mozilla Thunderbird email client.
Observed behavior: Thunderbird repeatedly requests a password or reports an authentication failure when attempting to sync with Hotmail or Outlook.com through OAuth2.

Before you start

Ensure you have your correct Microsoft account credentials and that your Thunderbird client is updated to the latest version, as older versions may not fully support modern OAuth2 standards.

Solution 1Recommended

Configure OAuth2 Authentication and Server Settings

Updating both incoming and outgoing authentication methods to OAuth2 is the standard fix for modern Microsoft email connection issues in Thunderbird.

Microsoft has deprecated basic password authentication for Outlook and Hotmail accounts. You must switch your Thunderbird account settings to use OAuth2 for both receiving (IMAP/POP) and sending (SMTP) emails.

Access Account Settings

Open Thunderbird, click on the application menu (three horizontal lines), and select 'Account Settings'.

Update Incoming Server Settings

Select 'Server Settings' under your Hotmail/Outlook account. Change the 'Authentication method' dropdown to 'OAuth2'. If you are using POP3, verify that the 'Port' is set to 995.

Update Outgoing Server (SMTP) Settings

Scroll to the bottom of the left pane and select 'Outgoing Server (SMTP)'. Select your Microsoft SMTP server, click 'Edit', and change the 'Authentication method' to 'OAuth2'.

Restart and Authenticate

Restart Thunderbird. Upon opening, a Microsoft login window will appear. Enter your Hotmail or Outlook credentials and grant Thunderbird permission to access your account.

Configure OAuth2 Authentication and Server Settings

Authentication Restored: Once permissions are granted through the Microsoft prompt, Thunderbird will save the OAuth2 token and stop repeatedly asking for a password.

Solution 2

Enable POP or IMAP Access in Outlook on the Web

Microsoft accounts may have third-party app access via IMAP or POP disabled by default, which blocks Thunderbird from syncing even if OAuth2 is configured correctly.

Solution 3

Reinstall Thunderbird (Caution)

If configuration changes fail, a clean installation might resolve deep-rooted authentication bugs, though it carries a risk of data loss if not properly backed up.

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Frequently Asked Questions

Why is Thunderbird repeatedly asking for my Hotmail password?

This usually happens because Microsoft has deprecated basic password authentication. Switching the authentication method to OAuth2 in Thunderbird's incoming and outgoing server settings will securely tokenize your login and resolve the prompt loop.

What port should I use for Hotmail POP3 in Thunderbird?

For a Hotmail or Outlook POP3 account in Thunderbird, you should use port 995 with SSL/TLS connection security, combined with the OAuth2 authentication method.

Will reinstalling Thunderbird delete my contacts and emails?

Uninstalling Thunderbird does not normally delete your profile data, which is stored in a separate directory. However, to guarantee you do not lose contacts or local emails, you should always back up your Thunderbird profile folder before proceeding with a reinstallation.

Outlook & Email Problems