Does the Exchange Server Recipient Update Service (RUS) require any kind of regular maintenance?

There isn't really much maintenance to perform on the RUS, but I do recommend that you monitor RUS behavior and performance. The RUS is responsible for maintaining address information about mail-enabled objects and for applying changes when you create or remove recipient policies (as described in the Microsoft article "XADM: How the Recipient Update Service Applies Recipient Policies" at http://support.microsoft.com/?kbid=328738). If the RUS stops working, such changes won't be applied correctly.

How can you tell if the RUS is behaving badly? Check out the Microsoft article "How To Verify That the Recipient Update Service Is Working Correctly" (http://support.microsoft.com/?kbid=821908), which details some steps that you can use to identify RUS problems and what to do about them. To monitor RUS performance, keep an eye on the RUS object's Address List Queue Length counter in Performance Monitor. A queue length that climbs and remains high compared with your usual operating baseline is a good sign that your RUS server is underpowered.