I got a mail in my outlook and the application didn't let me open the attachment because it might be unsecure. The mail was from a know person and I want to access the attachment file. It appears that you can override the security level as described by Microsoft ( Customize attachment settings in Outlook 2007) and let some file types allowed to be opened.
To do this you have to tell the outlook which types of files are allowed. You do it in the registry:
You simply mention the extentions seporated by a semicolon like this one :