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Change the Outlook Client Access Server


It could happen you should change the Client Access Server for Outlook, for instance if a CAS server is unavailable due to a hardware issue. In this blog I will discuss how to change the RPCClientAccessServer in such case.


You are using an Exchange DAG (Database Availability Group) with a minimum of 2 CAS servers (Client Access Server) without using a load balanced CAS array.

roles DAG member site status
Server 1 MB/CAS/HUB Yes A Failed
Server 2 MB/CAS/HUB Yes B Healthy


If server 1 fails all mailboxes will fail over to server 2. Because there is no CAS array configured Outlook can’t connect to Exchange anymore (The RPCClienAccessServer setting will point to the first installed CAS server by default, server 1 in this case).



To ensure the connection can be restored (to server 2) you will need to change the RPCClientAccessServer on every mailbox database.

To show the current RPCClientAccessServer setting run “get-mailboxdatabase <naam van de database> | fl RpcClientAccessServer”


If you are running multiple CAS arrays or want to change the RPCClientAccessServer for only one database this can be accomplished using the set-mailboxdatabase command.

More about RPC Client Access



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