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Offboarding mailbox fails with error: MigrationPermanentException Target user already has a primary mailbox

  • Article
  • Applies to:
    Exchange Online

Symptoms

Assume that you are in a Microsoft Exchange hybrid environment. When you try to offboard Exchange Online mailboxes to the on-premises organization by using the migration batch in Microsoft 365 Exchange Admin Center (EAC), the attempt fails, and you receive an error message that resembles the following:

'Error: MigrationPermanentException: Target user ‎'User‎' already has a primary mailbox.'.

Cause

This issue occurs because the HomeMDB and HomeMTA attributes are present on the user object in on-premises Active Directory, and they contain values.

Resolution

To fix this issue, follow these steps:

Step 1: Install Active Directory PowerShell Module, and then run either of the following PowerShell commands to review the values of the homeMDB and homeMTA attributes on the user object.

Command option 1

PowerShell 
Get-ADUser -Filter {userprincipalname -eq 'user@contoso.com'} -properties homemdb,homemta

Command option 2

PowerShell 
Get-ADUser -Identity 'SAMAccountName of the user' -properties homemdb,homemta

Step 2: Clear the values of the homemdb and homemta attributes. To do this, run either of the following PowerShell commands:

Command option 1

PowerShell 
Get-ADUser -Filter {userprincipalname -eq 'user@contoso.com'} -properties homemdb,homemta | Set-ADObject -clear homemdb,homemta

Command option 2

PowerShell 
Get-ADUser -Identity 'SAMAccountName of the user' -properties homemdb,homemta | Set-ADobject -clear homemdb,homemta

Step 3: Select the affected users in the migration batch, and then start the batch to move the users again. In this step, you could also use the following PowerShell command:

PowerShell 
Start-MigrationUser -Identity user@contoso.com