Configure Alias Domains in Azure AD

Oct 13, 2025 by wbrum.org 7 views

Quick Question on Domain Alias for Entra ID

Understanding the Challenge

We are excited to hear that you have successfully authenticated users from your Entra ID <domain>.onmicrosoft.com. However, we understand that you are facing a challenge with users using alias domains for their User Principal Name (UPN). This is a common issue that many organizations face, especially when they have multiple domains or subdomains.

The Issue with Alias Domains

In your case, users are using an alias domain for their UPN, for example, user@<domain>.onmicrosoft.com to user@domain.com. This can cause issues with authentication and authorization, as the system may not recognize the alias domain as a valid UPN.

The Goal: Making Realms Work with Alias Domains

Your goal is to make the realms work with an alias domain for the user. This means that you want to allow users to use their alias domain (e.g., user@aliasdomain.com) instead of their primary domain (e.g., user@<domain>.onmicrosoft.com). This will enable seamless authentication and authorization across different domains.

Possible Solutions

There are a few possible solutions to this issue:

1. Configure Alias Domains in Azure AD

You can configure alias domains in Azure AD to allow users to use their alias domain for authentication. To do this, follow these steps:

Go to the Azure AD portal and navigate to the "Domains" section.
Click on the "Add a custom domain" button.
Enter the alias domain (e.g., aliasdomain.com) and click "Add".
Configure the alias domain as a valid UPN suffix.

2. Use a Federation Service

You can use a federation service, such as Azure AD B2C or Azure AD B2B, to enable users to authenticate with their alias domain. This will allow users to use their alias domain for authentication, while still maintaining the security and control of your Azure AD environment.

3. Implement a Custom Solution

If the above solutions do not meet your requirements, you can implement a custom solution using Azure AD APIs or other third-party tools. This will require significant development and testing efforts, but can provide a tailored solution to your specific needs.

Conclusion

We hope this article has provided you with a clear understanding of the challenge and possible solutions to making realms work with alias domains for Entra ID. If you have any further questions or need additional assistance, please don't hesitate to reach out.

Additional Resources

For more information on configuring alias domains in Azure AD, please refer to the official Microsoft documentation:

We hope this helps, and we look forward to hearing from you if you have any further questions or need additional assistance.
Quick Question on Domain Alias for Entra ID: Q&A

Understanding the Challenge

Q&A: Making Realms Work with Alias Domains

Q: What is the issue with alias domains in Entra ID?

A: In Entra ID, users are using an alias domain for their UPN, for example, user@<domain>.onmicrosoft.com to user@domain.com. This can cause issues with authentication and authorization, as the system may not recognize the alias domain as a valid UPN.

Q: Can I configure alias domains in Azure AD?

A: Yes, you can configure alias domains in Azure AD to allow users to use their alias domain for authentication. To do this, follow these steps:

Go to the Azure AD portal and navigate to the "Domains" section.
Click on the "Add a custom domain" button.
Enter the alias domain (e.g., aliasdomain.com) and click "Add".
Configure the alias domain as a valid UPN suffix.

Q: What is a federation service, and how can it help with alias domains?

A: A federation service, such as Azure AD B2C or Azure AD B2B, can enable users to authenticate with their alias domain. This will allow users to use their alias domain for authentication, while still maintaining the security and control of your Azure AD environment.

Q: Can I implement a custom solution using Azure AD APIs or third-party tools?

A: Yes, you can implement a custom solution using Azure AD APIs or other third-party tools. This will require significant development and testing efforts, but can provide a tailored solution to your specific needs.

Q: What are the benefits of using a federation service for alias domains?

A: Using a federation service for alias domains can provide several benefits, including:

Seamless authentication and authorization across different domains
Improved security and control over user access
Enhanced flexibility and scalability for your organization

Q: What are the potential drawbacks of using a federation service for alias domains?

A: Using a federation service for alias domains can also have some potential drawbacks, including:

Additional complexity and overhead for implementation and management
Potential security risks if not properly configured and managed
Additional costs for licensing and support

Q: Can I use a federation service with multiple alias domains?

A: Yes, you can use a federation service with multiple alias domains. This will allow you to support multiple alias domains and provide seamless authentication and authorization across different domains.

Conclusion

We hope this Q&A article has provided you with a clear understanding of the challenge and possible solutions to making realms work with alias domains for Entra ID. If you have any further questions or need additional assistance, please don't hesitate to reach out.

Additional Resources

For more information on configuring alias domains in Azure AD, please refer to the official Microsoft documentation:

We hope this helps, and we look forward to hearing from you if you have any further questions or need additional assistance.