A. Outlook clients running MAPI RPC over TCP (or MAPI RPC over HTTP) communicate directly with the mailbox server. Outlook clients talk to a Client Access server to fetch client profile settings, free/busy data, and the offline address book. All other client protocols are via the Client Access server (e.g., IMAP, POP3, ActiveSync, Outlook Web Access--OWA). It's therefore possible to not have a Client Access server in a location if clients are MAPI only; however, the absence of the availability service (which is where free/busy comes from in Exchange 2007), the offline address book, and so on, would probably cause access problems.