On the University of Iowa Campus, the Global Address Book, or GAL, is displayed as the default Address Book in Outlook.

To change this in Outlook 2016:

1. From the main Outlook 'Home' window, select Address Book
2. In the Address Book window, select Tools | Options...
3. In the Addressing window, update the When opening the address book, show this address list first drop-down to the preferred list.
4. Click OK