Hybrid Exchange mailbox On-boarding : Target user already has a primary mailbox – Fix

During an Office 365 migration on a Hybrid environment with AAD Connectran into the following scenario:

  • Hybrid Co-Existence Environment with AAD-Sync
  • User [email protected] has a mailbox on-premises. Jon is represented as a Mail User in the cloud with an office 365 license
  • [email protected] had a cloud-only mailbox prior to the initial AD-sync was run
  • A user account is registered as a mail-user and has a valid license attached
  • During the office 365 Remote mailbox move, we end up with the following error during validation and removing the immutable ID and remapping to on-premise account won’t fix the issue
Target user 'Sam fisher' already has a primary mailbox.
+ CategoryInfo : InvalidArgument: (tsu:MailboxOrMailUserIdParameter) [New-MoveRequest], RecipientTaskException
+ FullyQualifiedErrorId : [Server=Pl-EX001,RequestId=19e90208-e39d-42bc-bde3-ee0db6375b8a,TimeStamp=11/6/2019 4:10:43 PM] [FailureCategory=Cmdlet-RecipientTaskException] 9418C1E1,Microsoft.Exchange.Management.Migration.MailboxRep
+ PSComputerName : Pl-ex001.Paladin.org

It turns out this happens due to an unclean cloud object on MSOL, This is because Exchange online keeps pointers that indicate that there used to be a mailbox in the cloud for this user

Option 1 (nuclear option)

to fix this problem was to delete *MSOL User Object* for Sam and re-sync it from on-premises. This would delete [email protected] from the cloud – but it will delete him/her from all workloads, not only Exchange. This is problematic because Sam is already using Teams, One-drive, SharePoint.

Option 2

Clean up only the office 365 mailbox pointer information

PS C:\> Set-User [email protected] -PermanentlyClearPreviousMailboxInfo 
Are you sure you want to perform this action?
Delete all existing information about user "[email protected]"?. This operation will clear existing values from
Previous home MDB and Previous Mailbox GUID of the user. After deletion, reconnecting to the previous mailbox that
existed in the cloud will not be possible and any content it had will be unrecoverable PERMANENTLY. Do you want to
[Y] Yes [A] Yes to All [N] No [L] No to All [?] Help (default is "Y"): a

Executing this leaves you with a clean object without the duplicate-mailbox problem,

in some cases when you run this command you will get the following output 

 “Command completed successfully, but no user settings were changed.”

If this happens

Remove the license from the user temporarily and run the command to remove previous mailbox data

then you can re-add the license 


MS Exchange 2016 [ERROR] Cannot find path ‘..\Exchange_Server_V15\UnifiedMessaging\grammars’ because it does not exist.

So recently I ran into this annoying error message with Exchange 2016 CU11 Update.

Environment info-

  • Exchange 2016 upgrade from CU8 to CU11
  • Exchange binaries are installed under D:\Microsoft\Exchange_Server_V15\..
Microsoft.PowerShell.Commands.GetItemCommand.ProcessRecord()". [12/04/2018 16:41:43.0233] [1] [ERROR] Cannot find path 'D:\Microsoft\Exchange_Server_V15\UnifiedMessaging\grammars' because it does not exist. 
[12/04/2018 16:41:43.0233] [1] [ERROR-REFERENCE] Id=UnifiedMessagingComponent___99d8be02cb8d413eafc6ff15e437e13d Component=EXCHANGE14:\Current\Release\Shared\Datacenter\Setup
[12/04/2018 16:41:43.0234] [1] Setup is stopping now because of one or more critical errors. [12/04/2018 16:41:43.0234] [1] Finished executing component tasks.
[12/04/2018 16:41:43.0318] [1] Ending processing Install-UnifiedMessagingRole
[12/04/2018 16:44:51.0116] [0] CurrentResult setupbase.maincore:396: 0 [12/04/2018 16:44:51.0118] [0] End of Setup
[12/04/2018 16:44:51.0118] [0] **********************************************

Root Cause

Ran the Setup again and it failed with the same error
while going though the log files i notice that the setup looks for this file path while configuring the "Mailbox role: Unified Messaging service" (Stage 6 on the GUI installer)

$grammarPath = join-path $RoleInstallPath "UnifiedMessaging\grammars\*";

There was no folder present with the name grammars under the Path specified on the error

just to confirm, i checked another server on CU8 and the grammars folder is there.

Not sure why the folder got removed, it may have happened during the first run of the CU11 setup that failed,


My first thought was to copy the folder from an existing CU8 server. but just to avoid any issues (since exchange is sensitive to file versions)
I created an empty folder with the name "grammars" under D:\Microsoft\Exchange_Server_V15\UnifiedMessaging\

Ran the setup again and it continued the upgrade process and completed without any issues...¯\_(ツ)_/¯

[12/04/2018 18:07:50.0416] [2] Ending processing Set-ServerComponentState
[12/04/2018 18:07:50.0417] [2] Beginning processing Write-ExchangeSetupLog
[12/04/2018 18:07:50.0420] [2] Install is complete. Server state has been set to Active.
[12/04/2018 18:07:50.0421] [2] Ending processing Write-ExchangeSetupLog
[12/04/2018 18:07:50.0422] [1] Finished executing component tasks.
[12/04/2018 18:07:50.0429] [1] Ending processing Start-PostSetup
[12/04/2018 18:07:50.0524] [0] CurrentResult setupbase.maincore:396: 0
[12/04/2018 18:07:50.0525] [0] End of Setup
[12/04/2018 18:07:50.0525] [0] **********************************************

Considering cost of this software M$ really have to be better about error handling IMO, i have run in to silly issues like this way too many times since Exchange 2010.