A button is used more and more as the CTA of an email campaign. However most marketers and coders were using images for aesthetic reasons.
The problem with that is that there is a high probability that the images will be blocked by the email provider and the recipients will not see anything. This why you should always style your ALT text, btw.
Stig Morten Myre has created a nice solution for the buttons that “need” a creative boost, using a background image that is repeating itself horizontally and falls back in a specified color when this doesn’t work. Add some rounded corners and you have a pretty nice result, acceptable result in most ESPs.
These buttons will NOT work everywhere, in some cases you will lose the rounded corners, in some the nice gradient, in some both. But it’s better than a text link, isn’t it?
Visit http://emailbtn.net/ for more info and the source code.