In an Exchange 2010 environment, you can control whether or not Outlook clients are required to use encrypted RPC connections. Since this cannot be configured from the Exchange Management Console, you'll need to use the shell in order to modify these settings. Use the steps in this recipe to control RPC encryption requirements using the Exchange Management Shell.
To enable RPC encryption for a CAS server, use the Set-RPCClientAccess cmdlet:
Set-RpcClientAccess -Server cas1 -EncryptionRequired $true
This enables RPC encryption for the CAS1 client access server.
In the RTM version of Exchange 2010, CAS servers were configured to require RPC encryption. Since Outlook 2007 and 2010 are configured by default with encryption enabled, those clients worked without any issues. On the other hand, many organizations are still running Outlook 2003, which by default is not configured to encrypt RPC connections. As such, since the RPC encryption...