I have a client with a single Static IP Address that exposes their Windows 2008 SBS server to the Internet for Email and OWA. They want to install a Cisco 5505 to allow for VPN access. Typically, when I set them up, I have the Cisco 5505 Outside Interface have an IP address that the VPN clients connect to. I then have another IP address that is routed through the Cisco Router as a Static Route to expose the SMTP and OWA services.
This client only has one IP address and I'm not sure if that can be done and what the configuration should be.