Fix App Password Authentication Problems in Outlook and Veeam
Question details
Users are experiencing invalid credential errors when attempting to use Microsoft 365 app passwords with Veeam email notifications or older versions of Outlook.
- Product
- Microsoft Outlook 2016, 2019, Veeam
- Device & OS
- not provided
- Scenario
- Configuring email notifications in Veeam or logging into Outlook using Microsoft 365 app passwords.
- Observed behavior
- The system throws an invalid credential error and rejects the app password during the authentication process.
Ensure you have your Microsoft 365 administrator contact information ready, as resolving app password and authentication issues often requires admin-level access to the Microsoft Entra admin center.
Transition to Modern Authentication (OAuth)
Since Microsoft deprecated Basic Authentication, switching to Modern Authentication is the recommended approach for secure logins without app passwords.
Basic authentication is officially deprecated in Exchange Online, causing traditional app passwords to fail frequently. Transitioning your email clients and Veeam setups to utilize OAuth or Modern Authentication prevents these invalid credential errors.
Open your Veeam Backup & Replication console or your Microsoft Outlook email account settings.
Navigate to the email notification or account configuration section and select the option to use Modern Authentication (OAuth 2.0) instead of Basic Authentication.
Follow the Microsoft 365 sign-in prompts in the pop-up window to securely authorize the application directly without needing an app password.
Verify Entra Security Defaults and Account Settings
If you must use app passwords for legacy apps, an administrator must confirm that Security Defaults are properly configured in Microsoft Entra.
Looking for a Lightweight Alternative to Microsoft Office?
If Microsoft 365 authentication and legacy login problems are slowing you down, consider switching to WPS Office. It is a powerful, free, and lightweight office suite that offers excellent compatibility with Microsoft Word, Excel, and PowerPoint formats without the complex administrative overhead.
Frequently Asked Questions
Why did my Microsoft 365 app password suddenly stop working in Outlook?
Microsoft has deprecated Basic Authentication for Exchange Online. This means older authentication methods, including app passwords, are being blocked by default to enhance security, requiring a shift to Modern Authentication.
Can I still use Outlook 2016 or 2019 with Microsoft 365?
Yes, but you must ensure that Modern Authentication is enabled for your tenant and that your Outlook client is updated to support OAuth 2.0 prompts instead of relying on legacy app passwords.
How do I set up email notifications in Veeam without an app password?
In newer versions of Veeam, you can configure email notifications using Modern Authentication (OAuth 2.0). This will prompt you to log in via a Microsoft 365 web window to authorize the connection securely without generating an app password.
Who can change my Microsoft Entra Security Defaults?
Only a user with Global Administrator privileges in your Microsoft 365 tenant can access the Microsoft Entra admin center to view or modify Security Defaults and legacy authentication policies.
