A different type of Active Directory object already exists error when migrating mailboxes in cutover migration

Original KB number:   2968722

Symptoms

When you perform a cutover migration to migrate mailboxes from your on-premises Microsoft Exchange organization to Microsoft Exchange Online, one or more users aren't migrated, and you receive the following error message:

A different type of Active Directory object already exists for "<user>@<domainname>.com" in the target forest. Please verify that the SMTP address is correct.

Cause

This issue occurs because user objects that weren't migrated already are located in the target Exchange Online organization.

Resolution

To resolve this issue, remove the user objects in Exchange Online. To do this, follow these steps:

1. Sign in to the Microsoft 365 portal as an admin.
2. Select users and groups, and then search for the users who didn't migrate.
3. Permanently delete the users. You can do this in the Microsoft 365 portal or by using the Microsoft Azure Active Directory module for Windows PowerShell.

Important

Deleting a user account will also delete the associated SharePoint Online and Skype for Business Online (formerly Lync Online) information for that user.

To delete users by using the Azure Active Directory module for Windows PowerShell, follow these steps:

1. Connect to Microsoft Entra ID. For more information about how to do this, see Microsoft Entra Cmdlets.

2. Run the following command:

   Remove-MSOL -UserPrincipalName User@domain.com -RemoveFromRecycleBin
   

After you follow these steps, make sure that users are no longer listed in the portal, and then perform the migration.

More information

For more information about cutover Exchange migration, see Migrate email using the Exchange cutover method.

Still need help? Go to Microsoft Community or the Microsoft Q&A.