How to grant Application Impersonation rights for Microsoft Exchange 2013/2016 (4352358)

To enable the Migration administrator account to impersonate users, the following will need to be run in Exchange Management Shell:

New-ManagementRoleAssignment -Role ApplicationImpersonation -User Migration Account

Below is a Microsoft article that explain more about granting impersonation rights.

To migrate from a hosted Exchange environment the RecipientOrganizationalUnitScope will need to be used to specify the OU of the users on Exchange server.

New-ManagementRoleAssignment -Name:MigrationImpersonationAssignment -Role:ApplicationImpersonation -User:userName -RecipientOrganizationalUnitScope "domain.com/Microsoft Exchange Hosted Organizations/company.com"

For more information on this Exchange 2013 command refer to the technet site: 

https://technet.microsoft.com/en-us/library/dd335193(v=exchg.150).aspx