When you try to migrate a user to Microsoft Office 365 Dedicated/ITAR vNext or you try to set up Unified Messaging in vNext, you receive one of the following error messages:
'Mailbox '<identity>' in the source forest is currently enabled for Unified Messaging but it can't be enabled for Unified Messaging in the target forest for the following reason: Unified Messaging isn't available in the target forest. Please fix the problem.'
UsageLocation validation error: the action 'Enable-UMMailbox', 'Extensions,Identity,Pin,PinExpired,SIPResourceIdentifier,UMMailboxPolicy', cannot be performed on user '<identity>'. This feature is not available in the location indicated in this user's UsageLocation.
Some countries restrict Unified Messaging according to local laws, and therefore this feature may be blocked from use in vNext. The feature may have been previously turned on in Legacy Dedicated but no longer be available in vNext.
To resolve the error, you can turn off Unified Messaging when you migrate to vNext or not enable this feature for new users in vNext who are in affected countries.