Unable to add exchange server target

We have below environment,

EV 10.0.4 on a Windows Server 2008 R2

SQL Server 2008 R2

Exchange Server 2007

I am unable to add the exchange server as archiving target. Permissions have been set for the EV Service account already. The Vault Service account is also local admin on the exchange server. The error message from the deployment scanner is as below,

"Enterprise Vault was unable to determine the installed version of Microsoft Exchange Server. Reason: The server doesn't exist or there was a permissions problem communicating with Active Directory."

Any ideas would be welcome.

Thanks!