A newsletter is pretty much a update notification used on blogs/websites to remind people to visit your website, and an advertisement of some sorts. The newsletter is where you automatically describe you and your websites abilities as  the design/template is it’s face. Setting up a complex html newsletter is inefficient, but a simple layout which you can google will directly give you a form which will subconsciously make people automatically click it. I found this great article which explains step by step the newsletter designs and will lead you through it’s coding.

http://www.sitepoint.com/article/code-html-email-newsletters/