How to Fix Microsoft 365 'App Password Required' Errors When Using Legacy Email Apps on Windows 11

Summary

This guide helps you troubleshoot and resolve: How to Fix Microsoft 365 'App Password Required' Errors When Using Legacy Email Apps on Windows 11. Follow the steps below to fix the issue.

Common Causes

If you have recently enabled Multi-Factor Authentication (MFA) on your Microsoft 365 account, you may find that older email applications—such as Outlook 2016, Thunderbird, or the Windows Mail app—suddenly stop working. This happens because these legacy apps do not support modern authentication methods. To resolve this, you need to generate an app password through your Microsoft account security settings.

Steps to resolve

Step 1: Access your Microsoft account security settings

1. Open your web browser and go to the Microsoft account security page.
2. Sign in using your Microsoft 365 email address and password.
3. Complete the Multi-Factor Authentication prompt if asked.

Step 2: Generate an app password

1. Select Advanced security options.
2. Scroll down to the Additional security section.
3. Locate App passwords and select Create a new app password.
4. A 16-character code will appear on your screen. Copy this code immediately.
5. Select Done to close the window.

App passwords are only displayed once. If you lose the code, you will need to generate a new one.

Step 3: Update your email application

1. Open your legacy email app (for example, Outlook or Windows Mail).
2. Go to the account settings or email account configuration menu.
3. When prompted for your password, delete your existing Microsoft 365 password.
4. Paste the 16-character app password you copied earlier.
5. Save the settings and restart the application.

If you cannot find the App passwords option

App passwords are only available if Multi-Factor Authentication is enabled on your account. If the option is missing, ensure you are signed in as the account administrator and that MFA is active.

If the app password is not working

• Ensure there are no spaces before or after the code when pasting it into your email app.
• Double-check that you copied the full 16-character string.
• Try removing the email account from the application entirely and re-adding it using the app password.

Microsoft is gradually phasing out support for legacy authentication. If your application continues to fail, consider upgrading to a modern email client that supports OAuth2, such as the latest version of Microsoft Outlook.

If you are still experiencing authentication issues after following these steps, please contact your IT support team for further assistance.

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