This is only one solution that can be protect Exchange 2007 client access role.

For Outlook Anywhere Setting:

I only working with Basic Authentication.

Modify RpcwithCert setting in IIS

Using Basic Authentication Method for outlook anywhere

Outlook 2007  Exchange Proxy Setting

Outlook 2007 to Exchange 2007 connection setting

The following refer website:

Valid Self-cert for ISA 2006

How to proxying Exchange 2007 OWA, ActiveSync, Outlook Anywere using ISA 2006