The user principal names (UPN) of users contain an Office 365 domain after synchronization

You use the Microsoft Online Services Directory Synchronization Tool to synchronize your local Active Directory Domain Services to Microsoft Office 365. However, after synchronization, the user principal names (UPN) of users contain the domain that is assigned to your company when you signed up for Office 365 instead of your company domain. For example, the email address of a user is as follows:

This behavior occurs if your company's domain is not added to and verified in Office 365 before you start and enable directory synchronization. If you start and enable directory synchronization before you add and verify your domain, user accounts are synchronized. In this case, Office 365 assigns users a third-level Office 365 domain. For example, it assigns the following domain: And after the domain is verified, the UPN of the user is changed accordingly. To determine what the UPN is, on a domain controller or on a computer where a Windows Server Administration Toolkit is installed, follow these steps:

1. Open Active Directory Users and Computers. To do this, click Start, click Run, type dsa.msc, and then click OK.
   
   
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2. Right-click the domain, and then click Find.
   
   
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3. In the Name box, type the user's display name, and then click Find Now.
   
   
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4. Double-click the user name in the search results, and then click the Account tab.
5. Under User logon name, note the domain part of user logon name. This is known as the UPN suffix. 
   
   
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We strongly recommended that you add and verify your domain in the Office 365 portal or by using the Microsoft Online Services Module for Windows PowerShell before you start and enable directory synchronization.

Make sure that users are synchronized from the on-premises environment to Office 365 by using the same UPNs and email addresses. All domains that are associated with users' UPN must be verified in your Office 365 subscription.

For example, if the on-premises UPN of a user is user@contoso.com, and the user's default email address is user@fabrikam.com, make sure that both the contoso.com domain and the fabrikam.com domain are verified.

Note the following scenarios:

• If the user does not yet have a license, and the domain is verified, the UPN is changed accordingly.
• If the user has a license, and the domain is verified, the following conditions occur:
  • The UPN does not change for non-federated users.
  • The UPN is changed for federated users.
  • The default email addresses are changed accordingly.
  • Alternative email addresses that use the verified domain are automatically added.

To update a non-federated user's UPN while they have a license, follow these steps:

1. Connect to Microsoft Online Services by using the Microsoft Online Services Module for Windows PowerShell
2. Run the following PowerShell cmdlet:
   
   Set-MsolUserPrincipalName -UserPrincipalName [CurrentUPN] -NewUserPrincipalName [NewUPN]

For more information about how to add and verify a domain in Office 365, visit the following Microsoft website: For more information about updating other synchronized attributes, click the following article number to view it in the Microsoft Knowlege Base: