Microsoft.com :- "ISA Server Feature Pack 1 delivers enhanced security and ease of use beyond that of traditional firewalls for email server, Web server and Exchange Outlook Web Access (OWA) deployments. Email server security is enhanced by the improved ability to help filter out unwanted email messages. ISA Server with Feature Pack 1 provides protection for remote Outlook users accessing Exchange Server over untrusted networks without a VPN. Improved authentication and protection from evolving types of Internet attacks enables ISA Server to better secure Web and OWA servers. New wizards, scenario walkthroughs and technical documentation make configuration easier and answer commonly asked questions"