Hello rojalina A newletter is a vehicle to deliver valuable content to your subscriberss....but the subscriber list is what you are after You can use newsletter to create links to your sites blog, or sales page It is a part of your intergrated marketing strategy Hope your business is going well Leo Hanes
A newsletter will have no effect on SEO at all - it's something you send in an email - nothing to do with search engines. If done properly (i.e. isn't spam) it will have an effect on traffic and conversions, which is what you're doing SEO for.