Martin Blackstone's List of Danger: "This is a list of the file types that you should consider blocking with your Exchange or SMTP antivirus scanner. Each of these file types can be executed and thus release a virus into your systems. There are two lists. The first is the basics. These are the 'must have' extensions to be blocked. Those extensions are considered critical to attachment blocking. The second is the full list. This list includes most file types that could be used against you. Choose your list depending on your environment and your users needs."