Your Opt-In List is Gold. On the internet and off, savy marketers know that being able to contact people who want to hear from them is the way to go. This process is called opt-in. People opt-in or subscribe to your list. They agree to hear from you and are free to unsubscribe, if they wish.
Marketing is a numbers game.
Build you list as large as you can. The more people you contact, the more response, traffic and sales you will create. There are services that will provide you subscribers for a fee, but many people have not been able to afford to pay for a large amount of opt-in subscribers. This is a group that helps each other get opt in email subscribers. I am using them with two of my newsletters.