Richard,
Entourage uses the legacy virtual directory structure under Exchange 2007, i.e. in Exchange 2003 the 4 directories used by OWA were Exchange, public, exchweb and exadmin, Entourage was coded to work with them, it does not know about the new owa Vdir in Exchange 2007, Exchange product group has put in an exception for Entourage in terms of redirection, when davex or exprox dlls see a request from Entourage for exchange and public Vdirs, they don't redirect, they let it go. If you have used Entourage with Exchange 2003, then you don't need to change anything, just change the server name and point it to your exchange 2007 server. Let's assume you are tryign to make this work for an internal user, who can ping the exchange 2007 server from his Mac using its NetBIOS name, now use the same NetBIOS name in Exchange and public folder server names fields in account settings in Entourage. On Exchange side, go to Exchange management console : server config : client access, set all 4 exchage legacy vdirs with basic and ntlm (integrated) authentication, now go to IIS > Defautl Website, make sure all those Vdirs are not requiring SSL for connection. You are all set then. If you want your users to use SSL for this connection, then you will have to work further, I recommend not using the self-signed Exchange 2007 certificate, rather a certificate from a known Root CA out there, if not possible, then install and use your own private root CA on your Windows global catalog server, you will need to make sure that its then trusted by your Mac clients. Let us know if this does not work.