I would hope that email newsletters have success, especially if you follow the advice of the previous posters. I tend to subscribe to newsletters on any website I enjoy, otherwise I will forget to return to that site! And if I'm in the mood to surf, I'll go to my email first...so if your newsletter was there, I'd go to your site.
To add a question to the mix, what would you write in a graphic designers newsletter? I would have a hard time coming up with content that potential (or current) clients would appreciate rather than things other designers would want to read.
-E
ETMDesign