You should maybe add a "Base href" to http://m2media.com to you mail body. It could be, that the image paths are just relative to the document (your mail body page) and not to the site, thus the images would not be visible in an email client such as thunderbird or outlook.
From your source code it looks, like this is the case:
<p><a href="http://m2media.com/home.html"><img src="images/m2_logo.jpg" width="100" height="111" alt=""/></a>
Instead of <img src="images/m2_logo.jpg" ....> you should use <img src="http://m2media.com/images/m2_logo.jpg" ....>
or add the base href, as described above.