This is a very short step by step guide of how to configure your Exchange 2007 CAS to provide RPC over HTTPs.
1- Install RPC over HTTP Proxy component (windows component)
2- Install a certificate on your CAS server (E2K7: How to generate and install a certificate for a CAS server) –
3- Enable Outlook Anywhere via console (server configuration/client access /select your server / right-click on your server / enable Outlook AnyWhere) –
4- External host Name should match the name issued to the certifcate installed on your CAS
5- Autodiscover should configure your OL 2007 proxy authentication settings