Microsoft Outlook has a design flaw that allows outbound HTTP requests to be made via a simple preview of a mail that is S/MIME-signed.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/65086/AKLINK-SA-2008-002.txt
Source: https://packetstormsecurity.com/files/65086/AKLINK-SA-2008-002.txt.html