SharePoint sends outgoing email as anonymous SMTP. Under Exchange 2003 this wasn’t much of an issue as all you had to do was allow the SharePoint server IP as an allowed relay under the SMTP virtual server. In Exchange 2007, however it becomes a bit trickier since Exchange 2007 has built-in security to make it more difficult to create open relays. First you have to create a custom receive connector with the IP addresses of your SharePoint front ends listed as allowed relays. Set your authentication...
The best practice for publishing an Internet facing SharePoint site is to use ISA as a reverse proxy solution to provide an additional layer of security between the SharePoint portal and the end user. This eliminates any traffic originating from the Internet from ever reaching the internal protected network. Instead the traffic terminates in the DMZ at the ISA server and it in turn performs Active Directory or Forms Based authentication through LDAP, LDAPS, or Radius. It then proxies the content...