Administering Recipient Update Services
Recipient Update Services, also known as RUS, are used to apply SMTP domains to recipients residing in domains where Exchange Server 2003 is not installed. The RUS is also responsible for managing and maintaining address list membership and updating address changes to ensure that accurate information is available at all times.
When installing Exchange Server 2003, each Exchange organization is installed with a default RUS. When installed, the default service contains two individual services. One is responsible for managing mail addresses and lists at the enterprise level, and the other is responsible for doing so at the domain level.
When working with multidomain environments, it is not always cost-effective ...