We talk a lot about how alt attributes come in handy for visually impaired Internet users. But what if you are getting your email in gmail, which defaults to not displaying images in a newsletter? And what if you send a beautiful email that is all an image? This is a very popular technique with Anthropologie's enewsletters. Unless the gmail user clicks the link at the top of their message window that says: "Always show images from this source," which allows the image to display, the potential customer could very easily miss your message.
However, if you filled in your alt attribute for at least the first image in your newsletter, and wrote some informative copy in it, like: "Christmas sweaters are now in stock!" vs "splash image," you may have caught the attention of your reader before they clicked Delete. Better yet, if you linked your image to the page where the reader can find this information, the alt attribute will also be linked, allowing the person to click on that catchy sentance.