Outgoing Email , Recipients Can Not View

Whenever I send an email with pictures embedded in the body of the email, all the recipient sees is a bunch of red x's. Typically, what I am sending is a forward of something someone else sent to me. Since I received and viewed the pictures just fine, clearly the problem is not in how the pictures are in the email. The preview of my outgoing email always shows the pictures just fine. But the recipients never can view them.

I have a Vista computer, and am using Windows Mail with my Cox email account. My wife is on the same computer. We have separate user accounts. She has the same setup as me - Windows Mail with her Cox email account. The security software is Microsoft Security Essentials. We had previously been using McAfee. My problems remained the same under both softwares. My wife has had no problems with sending pictures. She will receive the same email as me, forward it to someone else, and they can vie the pictures just fine. She can forward an email to me, and I can view the pictures. But if I forward that email back to her, like everyone else, all she sees is red x's.