You can advertise your product in other businesses’ newsletters that cater to your target audience. This technique can work well and it can bomb. I don’t advise this for beginners, as there are more cost effective, longer lasting methods of promoting your website.
However, if you feel compelled to advertise in a newsletter, do LOTS of research ahead of time. Find out as much as you can about the newsletter. Look for testimonials from past advertisers, and compare their products with yours. Make sure your product is a good fit for the eZine you choose to advertise in. I strongly recommend that beginners not bother with advertising in other people’s newsletters unless they are advertising for free or next to nothing.