RPC Endpoint issue with Exchange 2010

Hi,

I have a problem with Outlook Anywhere clients. When I run a ERCA test it fails on:

Attempting to ping RPC endpoint 6001 (Exchange Information Store) on server CASSERVER.internal.domain.

I checked the RPC ports on the server, I connect to all of them via telnet. Should the server name above be the external or the internal domain name though? I get a successful RPC Proxy ping.

Another thing I think it might be is  the connection between the CAS server and the Mailbox server. I can't telnet ports 6001-6004 on the mailbox server. Where would be the correct place to open them, in the registry under \Rpc\RpcProxy?

Thanks