PowerShell Script – Give User Full Access Permissions to All mailboxes

This KB will show you how to give admin user full access permissions to all mailboxes In the organization.

The script will work on Exchange Server 2007, 2010, 2013 and 2016.

 get-mailbox -ResultSize unlimited | Add-MailboxPermission -User     
 administrator -AccessRights fullaccess

One done you will see the permission that were added

To reverse the permissions use the same script just use Remove-MailboxPermission