How to use UPN of Entra ID user as email id to send or receive emails ?

Sohrab Hussain 0 Reputation points

I am trying to set up email at my custom domain. I have added a custom domain successfully and created a user in Entra ID. Also, I have enabled Use UPN as alternate email option in MS Entra Connect - Connect Sync - Email as an alternate login ID, When I am trying to login into outlook email, with this user, it is not logging in.

Please help, if anybody faced similar issue.

Microsoft Entra
Microsoft Entra ID
Microsoft Entra ID
A Microsoft Entra identity service that provides identity management and access control capabilities. Replaces Azure Active Directory.
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  1. Carlos Solís Salazar 14,866 Reputation points

    Using the User Principal Name (UPN) of an Entra ID user as an email address to send or receive emails involves several steps, especially if you're setting up a custom domain and integrating it with Microsoft services. Let's break down the process and see where the issue might be occurring in your case.

    1. Adding and Verifying Custom Domain: First, ensure that your custom domain has been successfully added and verified in your Microsoft 365 admin center. This process typically involves adding DNS records provided by Microsoft to your domain registrar's website.
    2. Creating Users with Custom Domain UPN: After your domain is set up, you can create users in Microsoft Entra (formerly Azure AD) with UPNs that reflect your custom domain (e.g.,
    3. Configuring Email Service: If you want these users to use Microsoft Outlook for email, you need to have a subscription to a service that includes email hosting, like Microsoft 365 Business or Enterprise. Simply having a custom domain in Microsoft Entra doesn't automatically provide email hosting capabilities.
    4. Setting UPN as Alternate Email ID: The setting for "Use UPN as alternate email" in Microsoft Entra Connect Sync allows users to log in with their UPN, but this doesn’t necessarily mean their UPN is configured to receive emails unless the email service is set up for those UPNs.
    5. Assigning Licenses: Ensure that each user has been assigned the appropriate Microsoft 365 license that includes email services (like Exchange Online). Without an appropriate license, users won't have an active mailbox to use with Outlook.
    6. Testing Login to Outlook: After setting up the above, users should be able to log into Outlook using their UPN. If login fails, check for any error messages. Common issues include incorrect password, the need to propagate DNS changes (which can take up to 48 hours), or not having the correct licenses assigned.
    7. Troubleshooting: If you continue to face issues, use the Microsoft 365 admin center to troubleshoot. Check the user's profile to ensure everything is set up correctly. You can also use the Microsoft 365 Support and Recovery Assistant, which can diagnose and resolve many common Outlook problems.

    If these steps don't resolve your issue, you might want to reach out to Microsoft Support directly, as they can provide more targeted assistance based on your specific configuration and subscription details.

    Remember, setting up a custom domain and configuring email services can be complex, and sometimes it might require some patience, especially when it comes to DNS propagation and license assignment.

    If you need further assistance or have more questions, feel free to ask. I'm here to help you through this process!

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