In order to make Outlook 2003 connections easier to complete, we changed the mailbox server name to give the appearance of connections to different mailboxes on different servers. Only the AddressBook service understands this changed mailbox server name. Therefore, clients that try to connect directly to Active Directory will fail to make the connection.
However, if many delegate mailboxes are being used, clients that are accessing the Address Book Service will reach a limit on the number of connections any single user can have. This exhausts the maximum number of connections available (20) specified by the default throttling policy that is associated with the user mailbox.
In this situation, Outlook 2007 clients and later-version clients do not open multiple additional connections.
After you make this change, wait for the Active Directory replication to finish. By default, the throttling policy should be applied after 15 minutes. To apply it immediately, restart the Microsoft Exchange RPC Client Access service on the Client Access Server (CAS).
Note An RCAMaxConcurrency value of 100 is sufficient in typical cases in which Outlook 2003 has to open 29 shared calendars. This value may have to be increased, depending on which Outlook add-ins are installed.
Important The original release of Exchange Server 2010 allows a maximum parameter value for RCAMaxConcurrency of 100. Exchange Server 2010 Service Pack 1 increases the maximum value for RCAMaxConcurrency to 2147483647.
Article ID: 2299468 - Last Review: Dec 7, 2010 - Revision: 1