Error -2147024809 The parameter is incorrect. : CExchAttendantCalls::ConnectEx failed! File: 'aeExchRpc.cpp' Line: '154' in the Calendar Synchronization Agent log file (4254396)

Calendar Synchronization Agent (CSA) fails to synchronize data to the target Exchange 2010 server from an Exchange server of an older version, and the following errors appear in its log:

Error -2147024809 The parameter is incorrect.  : CExchAttendantCalls::ConnectEx failed! File: 'aeExchRpc.cpp' Line: '154'
Warning 1722 The RPC server is unavailable. Server name - <CSA_agent_host_name>, service name - Quest Migration Attendant for Exchange service.

This combination of errors appears in log if CSA is running on an agent host in a source AD forest and tries to (re)create a mailbox on the target Exchange server. When CSA performs this operation against an Exchange 2010 server, it relies on the Migration Attendant for Exchange service on the local machine in doing that. However, this component is only installed on agent hosts associated with Exchange 2010 servers. Therefore, CSA fails to find it on the local agent host and is unable to (re)create a mailbox.

Note that the QMM for Exchange 8.10 documentation (see http://documents.software.quest.com/DOC82094#ExchangeMigrationAgents) states the following for standalone agent hosts (excluding Migration Agent for Exchange):

• Exchange 2010 Management Tools with the latest available updates (see the note below)

Note: Exchange 2010 Management Tools are required only for agent hosts where Mail Source Agent (Remote User Collections only), Mail Target Agent , or Calendar Synchronization Agent instances processing Exchange 2010 servers are installed. Note that installation of Exchange 2010 Management Tools requires  Active Directory schema extension. If that is not appropriate, install those agents on the agent host associated with the target Exchange Server 2010.

The primary recommendation is to revise your deployment of Migration Manager for Exchange components deployment to meet the above mentioned requirement for the CSA host.

If you have specific reasons why this requirement cannot be followed in your network, you can follow the following steps to resolve the problem in the alternative way:

1. Install the QMM for Exchange 8.10 Public Update 20150211EX or a later one and verify that it is propagated to the deployed agents as described in the ReadMe document shipped with the Update.
2. In QMM Console, find the name of the target Exchange server of your Calendar Synchronization collection under Target Exchange Organizations and open its Properties. Find the name of the agent host specified on the Default Agent Host page there.
3. If the default agent host of the target server is not actually involved into migration and does not have any agents installed, check that it meets the system requirements and deploy at least one agent on that host. There is no need to use or even start that agent. The only goal of this operation is to have Shared Components deployed on the host. As an alternative, consider specifying a different agent host as the default one for the target Exchange server.
4. Add the following line to the Config.ini file of each instance of CSA involved into this scenario:
    UseRemoteAttendant=1
   Save the file and restart the instance of CSA for the change to take effect.

After you do that, CSA will be "talking" to the Migration Attendant for Exchange on the agent host associated with the target Exchange server (its Default Agent Host) when it needs to create a target mailbox, and not to the one installed locally as it does by default.