We recently were performing a migration from a hosted Exchange platform to an on-prem Exchange 2013 deployment due to an acquisition, and since it involved hosted Exchange we defaulted to MigrationWiz. As our customer was security conscious, they only wanted to give the MigrationWiz service account permissions to the mailboxes it needed access to. Luckily we’d just completed the AD portion of the migration using Migration Manager for AD so we had all the users in the same OU, which made this quite simple to accomplish in a single line of PowerShell.
Simply gather the location of the OU, the name of your MigrationWiz service account and substitute them appropriately, then execute this cmdlet in Exchange Management Shell in the target environment.
Get-Mailbox -OrganizationalUnit “OU=Users,DC=domain,DC=com” -ResultSize Unlimited | Add-MailboxPermission -AccessRights FullAccess -User MigrationWiz
As always, feel free to reach out to us if you run into any issues.