Some things should be simple. Like just right clicking the GAL in the EMC and selecting update. Then updating Outlook. But Nooooooo… do you think that actually works when you need it to?! Of course not.
So, fire up the Exchange Management Shell —
PS> Get-OfflineAddressBook | Update-OfflineAddressBook
PS> Update-FileDistributionService -Identity YourCASServer
Head on over to Outlook and download the address book and your changes should be there.