Click on the contact folder that you want to use as "Addressbook", right
Mouseclick/Properties/Outlook Addressbook/"
Activate the flag for "Show this folder as Outlook Addressbook".
If you want to have this folder as the default Addressbook, if you click on
the "To" field, you can change this in Outlook under
"Tools/Addressbook/Tools/Options", under "Show this folder first" select the
contact folder you want to have as first folder.