The Global Address List contains a listing of all addresses stored in the organisational addressbook. If your target is accessible through MAPI/HTTP you can list or download the GAL.

To list:

./ruler --email user@targetdomain.com abk list"

This will display all entries on screen. Now there can be ALOT of entries, so it's probably more useful to dump this list to file for offline parsing. To do this use the dump command.

./ruler --email user@targetdomain.com abk dump --output /tmp/gal.txt