Microsoft Exchange Server 2003 – RUS (Recipient Update Service)

Introduction to Microsoft Exchange Server 2003 – RUS

Some acronyms just trip of the tongue – RUS (Recipient Update Service) is a case in point.  In Exchange 2003 server, RUS’s main job is building the address lists.  However, RUS also creates the email address that you see on the user’s properties sheet.

Topics for RUS (Recipient Update Service)


Purpose of RUS in Exchange Server 2003

RUS works hand in hand with GAL (Global Address List).  Together they generate the list of addresses that users see in Outlook.  I think of Exchange 2003’s RUS as a little engine which runs an LDAP query, the results are to build or update the Users’ property sheets and the Address Lists.

Here is a list of the jobs that RUS performs:

  • Updates proxyAddresses attribute controlled by recipient policies. 
  • Initializes the homeMDB, homeMTA and msExchHomeServerName attributes.  Also the legacyExchangeDN and msExchMailboxGUID if appropriate.
  • Sets the showInAddressBook (or hideDLMembership).
  • Sets the ACL on the Microsoft Exchange System Objects (Check with ADSI Edit)
  • Populates the group called Exchange Enterprise Servers in Active Directory.


Exchange 2003 Server RUS (Recipient Update Service)

RUS interacts with Active Directory.  In the above diagram you can see how the Recipient Update Service (CPEXCH) is responsible for rebuilding just the domain address lists.  Whereas the (Enterprise Configuration) highlighted in the diagram, is responsible for updating the entire Active Directory Forest.

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RUS Timings

Exchange’s RUS is only as good as the Active Directory information on the domain controller.  While RUS suffers more than most services with latency, to be fair, if the Windows 2003 operating system was constantly checking every attribute of every object in Active Directory, then there would be no time for useful work.

Update Now – Recalculates the Exchange 2003 address list memberships.  By default RUS recalculates every 15 minutes, so pressing the button can save you waiting and wondering if it worked.

Rebuild – Starts from scratch, rechecks any new extension for example, changing CPEXCH.NET –>  Beware that on a production Exchange 2003 server this could take hours.

Re-home RUS (Recipient Update Service)

The time may come when you have to de-commission the Exchange Server which houses RUS.  If you need to move the RUS service to another server, then click on the General tab, next to the Exchange server box and then click Browse.  Next, in the Select Exchange Server dialog box, click the name of the new Exchange 2003 Server which will host the Recipient Update Service.

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Problem with RUS in a large Forest

I would like to share a bizarre problem with you.  When a company created new users, sometimes those people had mailboxes and sometimes not.  The heart of the problem was that they were a multi domain organization and one domain had user accounts, but no Exchange 2003 servers.  (The other domains all had Exchange 2003 servers).  What happened was that when they created users in the domain with no Exchange 2003 they pointed the mailboxes to a different domain.

Now for the solution, launch the Exchange System Manager and create RUS in the domain with no Exchange servers.  Strange, but true – it solved the problem of the mailbox enabled users with no email address.  For me the magic moment was when a new RUS was born, I had no idea that you could create more Recipient Update Services with Exchange System Manager.

Summary of RUS in Exchange Server 2003

Microsoft Exchange 2003’s RUS is your friend.  Call for RUS when you need to rebuild the address book or add secondary email addresses to mail objects.  If you need to Update Now or Rebuild, then navigate to the Recipients folder in the Exchange System Manager.

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