First, the author must in some way prove themselves, and secondly, to prove himself as something, a certain audience, trust which you want to win. And in order to comply with all two points, take time and a useful free stuff. And no one as newsletter does not help you to fully cope with this task. Concurrent two things. Filled with useful content site and by sending the same content, reach out to your audience. Thereby increasing the audience visiting your site and the base of your subscribers. These men are your potential buyers. But most importantly they will be your best mates.
As the content of your site interesting and useful author materials, in addition to increase attendance of your site, increases in proportion to the exchange of information and feedback from your audience. What does it mean to you as the site owner? You will ask questions based on you'll find topics for your new products and will know exactly what your subscribers are interested in what they are looking and want to know your visitors. In addition, you can ask your subscribers themselves, what they would like know what to learn. This allows you to conduct your market research. And as a consequence of the above, you, as owner of the site through its newsletter, providing useful material, can promote both their and partnership items. That is, as you probably noticed, in this case the goods are already secondary. Main visited site filled with useful material, newsletter, has a specific audience and feedback from this audience.