Outlook Express 6 question

  I scanned a picture into my PC and sent it to a friend.  When the friend opened the picture, it contained a lot of porn along with the  picture I sent.  After told wrote and told me about the porn, I made sure I had the latest updates and then in safe mode, I ran a quick scan and a full system scan using NIS 2009, a full system scan using Malwarebytes' Anti-Malware and a full system scan using SUPERAntiSpyware.  All of the scans came up clean, not even a tracking cookie.

  I don't know what program they used, but they wrote back and said their system was clean also.

  Can porn or any malware be attached to a mail message, when it is in route between the sender and the receiver?  Is there another program I can use to check my system?

 

  Still confused...