Change explicit User Principal Names to match Office 365 domain suffix

Most Enterprise Office 365 clients will use Active Directory Federation Services and Windows Azure Active Directory Sync, also known as DirSync for Single Sign-On functionality with Office 365.

Standard AD FS will use the on-premises UPN to access services in Office 365. Therefore Microsoft advises to make sure User Principal Name suffixes and e-mail adress suffixes match to make life simpler. Most ADS domains still use an internal routable domainname for instance contoso.local. However when implementing AD FS with Office 365 it permitted to have an “internet routable” domain suffix for instance contoso.com.

The best solution for this before implementing and running a DirSync is to create a new User Principal Name suffix to match your Office 365 domain suffix. This can be done by adding a new UPN suffix by going to:

  1. Open Active Directory Domains and Trusts
    2. Right click on the top level of the tree in the left pane and select properties
    3. Add the new internet routable UPN suffix e.i. contoso.com

Next step is to change the explicit User Principal Names for all the designated user objects in Active Directory which you plan to synchronize to Office 365. The easiest way to do this is with the help of allmighty PowerShell.

I wrote this easy one-liner which allows you to target a specific OU in Active Directory. Don’t forget to use the Active Directory Module for PowerShell.

Get-ADUser -Filter * -SearchBase ‘OU=Users,DC=fabrikam,DC=local’ -Properties userPrincipalName | foreach { Set-ADUser $_ -UserPrincipalName “$($_.samaccountname)@contoso.com”}

After succesfully running the cmd-lets you will notice the new UPN suffix is configured for the targeted user objects in ADS.

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