On Exchange Server 2007, RPC over HTTP access is called Outlook Anywhere. RPC over HTTP access is provided by Exchange Server 2007 with Client Access Server (CAS) installed. No Enterprise Vault Extensions are required on Exchange Server 2007, but you need to configure RPC over HTTP access on the Enterprise Vault server.

Outlook on users' computers needs to be configured to use RPC over HTTP, and Enterprise Vault Outlook Add-Ins (any type) need to be installed on users' computers. See the Setting up Exchange Server Archiving manual for instructions.