This is something I have tried with another client and it has been a huge success. I basically added a new checkbox to my submit form for users to signup to a newsletter about SEO and to my surprise a lot of people have been opting into it. The system automatically emails my client and provides the emails to add to his newsletter. I can set this up for you on my other site as well. Please let me know if you have a professional newsletter and let me know how much you are willing to pay for such a feature. Please send me a pm as I will only allow one newsletter addon per site so only three spots available.