Mailbox Connection issue due to RPCClientAccessServer Value in Mailbox Databases:

Recently our client acquired a business from another company and planned to setup new organization. The old organization has Exchange 2007 and Enterprise Vault 10 with the policy to archive emails prior to 6 months. The average size of each and every mailbox will be 1 GB.

We have the setup of Exchange 2010 with 2 Mailbox Servers (EXCH-MBX01 & 02), 1 HUB (EXCH-HUB01) Server and 1 CAS (EXCH-HUB02) server then mailbox databases (MDB01, 02, 03 & 04) have been created in Exchange 2010 and added to the DAG named EXCH_DAG1.ABC.COM.

The old organization exported 6 months’ content in all the user mailboxes from XYZ.COM domain and shared those PST file to us. We have created mailbox for all those users in new exchange setup and imported the content in the PST to the new mailboxes.

After few weeks we planned to add a MBX, HUB & CAS server to the existing setup and successfully added a MBX (EXCH-MBX03), HUB (EXCH-HUB02) and CAS (EXCH-CAS02) servers then created a CAS Array named PROD_CAS.ABC.COM and added those 2 CAS servers to the newly created CAS Array.

After we have completed the CAS Array setup, the CAS server EXCH-CAS01 went to Offline state and received call from the users that outlook is not working. As EXCH-CAS01 is in Offline State, so all the existing connection & new connection should route to EXCH-CAS02 using CAS Array but unable to connect their mailbox.

After we have verified the mailbox databases, we found that CAS Array detail is not updated in the mailbox databases. As we have created mailbox databases before the creation of CAS Array, RPCClientAccessServer value in all the mailbox databases have been automatically updated with the CAS server EXCH-CAS01. So mailbox in Exchange 2010 is accepting connection only through EXCH-CAS01 instead of CAS Array.

PS Command to verify RPCClientAccessServer detail in all the mailbox databases:

Using the PS Command below updated RPCClientAccessServer in all the mailbox databases then outlook automatically established connection to the mailboxes and working as expected.

Thank You 