What does RUS do in Exchange?

What does RUS do in Exchange?
RUS (Recipient Update Service) is responsible for making updates to e-mail addresses, and it does this based on recipient policy changes. These updates are made at a specific interval that is defined for the service. You can view the update interval and modify it as necessary by completing the following steps:
Start System Manager, and then in the left pane (the console tree), click the plus sign (+) next to the Replication node. Then select Recipient Update Service.
You should now see the available Recipient Update Service in the right pane. You will have an enterprise configuration service and one or more additional services for additional domains in the domain forest.
Right-click the service you want to work with, select Properties, and then use the properties dialog box to view the service's configuration settings.
Use Update interval to choose a new update interval. The following options are available:
Always Run
Run Every Hour
Run Every 2 Hours
Run Every 4 Hours
Never Run
Use Custom Schedule
Recipient Policy can also be manually updated at specific interval. You may want to do the following steps:
Start System Manager and then, in the left pane (console tree), click the plus sign (+) next to the Replication node, and then select Recipient Update Services.
You should now see the available Recipient Update Services in the right pane. You will have an enterprise configuration service and one or more additional services for additional domains in the domain forest.
Right-click the serrvices you want to work with, and then select Update now.