How to have the address book default to the Global Address Book
Microsoft Outlook – How to have the address book default to the Global Address Book:
You can change the default via the following steps;
Open the Address Book by pressing CTRL+SHIFT+B or for Outlook 2010, Outlook 2013 and Outlook 2016 - Use the Address Book icon on the right side of the Home tab in the Ribbon
In the Address Book dialog choose Tools-> Option
Use the dropdown list for “When opening the address book, show this address list first”
Set to Global Address List and press OK
Close the Address Book dialog.
Your default has been set!