Serving an image

Hello all. I am sending an email with a logo at the top of the email. The source of the image for the logo is: http://myurl.com/image.php?id=5 Image.php then calls a function that simply returns the following: $image='<img src="http://myurl.com/images/logo.jpg" />'; return $image; Calling the page directly via the URL http://myurl.com/image.php?id=5 works fine. But when the email is opened, I get the broken link/image icon even though I can see in my source that the URL which works when loaded into a browser. What needs to be done to serve that image to a email client when it is opened? Thanks, --Rick