Hello,   I am interested in purchasing opt-in users for my email list. These users will be presented with an Ad to join my newsletter, on a 3rd party website (co-regstration). The user will specifically be presented with the question, "Do you want to sign up to newsletter X'," so I believe that falls within the Terms and Conditions of Constant Contact.    In the past, I have used a pre-ping URL and a post URL to accomplish this. First the 3rd party would use the pre-ping URL to ping my system to see if an email address already exists. If it does not (returns a specific response), then they would then use the post URL to send the opt-in user information directly into my database, which then would then trigger my first welcome email to that user.    I know I'm getting the user's consent to email them, but obviously I can't apply a plugin to this 3rd party website's sign up form. Does anyone have any experience maybe using the API to accomplish what I'm looking to do? ... View more