RPC_S_SERVER_UNAVAILABLE (0x6BA) error code when you use a MAPI or CDO-based application in an Exchange Server 2010 environment


Consider the following scenario:

  • You use a MAPI or Collaborative Data Objects (CDO)-based application to log on to a mailbox in a Microsoft Exchange Server 2010 environment.

  • Your user account is the last logon object on the remote procedure call (RPC) connection.

  • The application does not send a remote operation (ROP) request for more than 2 minutes.

  • The¬†application tries to log you off from the mailbox.

In this scenario, the Microsoft Exchange RPC Client Access service throws a ServerUnavailableException exception. Additionally, the RPC_S_SERVER_UNAVAILABLE (0x6BA) error code is returned in the application.


To resolve this issue, install the following update rollup:

2803727 Description of Update Rollup 1 for Exchange Server 2010 Service Pack 3


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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