It might be interesting to add a click event on the link in the image and track how many people actually "click here" on the image of an inbox.
Maybe even have a popup that triggers if that link is clicked that says something like: "Sorry, this is just a screenshot. Please check your email inbox for this message"
http://i.imgur.com/d98aC.jpg
That is, downsized screenshot, with graphics drawn on top. I think the original looks too much like a real window.