Outlook enforces two file attachment security levels by default, level 1 and level 2.
Any file attachment that belongs to a Level 1 file extension is blocked and can't be viewed or accessed by a recipient.
Any e-mail message that contains a Level 2 file attachment prompts Outlook to ask users to save the file attachment to their hard disks. Level 2 file attachments cannot be opened directly from e-mail messages.
This addon allows the end user to move file types from a level 1 setting to a level 2 setting so that you can interact with blocked files within the Outlook application.
To use: Download the application and run the setup program. Then restart Outlook and select the options menu from the tools drop down. There will be a new tabbed labeled File restrictions. Use this interface to add/remove file types from the level 2 group.