Creating opt-in lists is easy when you use the web form tool that embeds on your site. As users sign up and subscribe, you will be automatically building a targeted list with as much detail as you want. Optionally activate double verification that forces users to activate their subscription or registration by clicking a link in their registered email. The system will also track the users IP address and date of email confirmation to keep your list building compliant.
Segmenting lists based on certain actions and triggers will help build even deeper, targeted lists. This can be done automatically, if you set it up properly. By defining the trigger rules to automatically add a recipient to a list based off a specific link click will help build your targeted list of contacts that have specific interests.