When you perform a cross-forest mailbox move from Microsoft Exchange Server 2007 to Microsoft Exchange Server 2013 by running the New-MoveRequest cmdlet together with the RemoteLegacy parameter, the process fails, and you receive an error message that resembles the following:
[PS] C:\Windows\system32>New-MoveRequest test01 -TargetDatabase:mdb01 -RemoteLegacy -RemoteCredential:$remoteCred -RemoteGlobalCatalog:domain.local -TargetDeliveryDomain:e.local
Recipient 'domain/OU/User' isn't a mailbox.
+ CategoryInfo : NotSpecified: (:) [New-MoveRequest], RemotePermanentException
+ FullyQualifiedErrorId : [Server=Server,RequestId=Request ID,TimeStamp=Date & Time] [FailureCategory=Cmdlet-RemotePermanentException] 435D5946,Microsoft.Exchange.Management.RecipientTasks.NewMoveRequest
+ PSComputerName : Computer Name
Recipient 'domain/OU/User' isn't a mailbox.
+ CategoryInfo : NotSpecified: (:) [New-MoveRequest], RemotePermanentException
+ FullyQualifiedErrorId : [Server=Server,RequestId=Request ID,TimeStamp=Date & Time] [FailureCategory=Cmdlet-RemotePermanentException] 435D5946,Microsoft.Exchange.Management.RecipientTasks.NewMoveRequest
+ PSComputerName : Computer Name