The GAL contains all Exchange recipient objects in the entire organization and is retrieved from the global catalog servers.
Default address lists are created from a specific set of attributes of recipient objects. Exchange provides five default address lists: All Contacts, All Groups, All Users, Public Folders, and the Default Global Address List (GAL).
The default offline address list is available to Exchange users when they are working offline with an Offline Folder and is created from the GAL.
You must associate each offline address list with a specific mailbox store this allows the offline users of that store to download it for usage offline.
By using the Open Address List permission, you can prevent your users and groups from viewing the contents of a custom address list.
The RUS is a service that is installed with Exchange Server and is responsible for building and maintaining all Exchange address lists.
RUS is also responsible for updating the email addresses of recipient objects based on settings that are configured in recipient policies.
The RUS update operation forces all address list memberships to be recalculated for recently modified Exchange recipients. The RUS rebuild operation forces all address list memberships to be recalculated.
