Active Directory Rights Management Services can be used to exchange rights-protected information over an extranet connection ...

Active Directory Rights Management Services can be used to exchange rights-protected information over an extranet connection with another organization that has also deployed an AD RMS cluster. To support this, an extranet cluster URL must be configured to allow a connection to AD RMS services over the Internet. This URL is also used by features such as Outlook Web Access and Outlook RPC over HTTP that support mobile users outside of your organization's network.