See: Remote Web Workplace Part 1 (PDF) for more info
Configure Internet and Email access settings to allow access to the Remote Web Workplace web service from the Internet (Server Management -> Connect to the Internet -> Web Services Configuration)
Configure the IIS Web application named Remote to Allow access by Default ( ISS Manager -> Web Sites -> Default Web Site -> Remote -> Properties -> Directory Security -> IP address and Domain Name restrictions -> Edit)
Configure the Firewall to allow SSH (Port 443) to the SBS box from the WAN. Create a custom service for RWW (Port 4125) and allow access to that service from the WAN to the SBS box.
Connecting client machines must be Windows XP Pro or better