An authentication method that requires a human to respond to an email challenge message before the original email that triggered the challenge is delivered to the recipient. This method is sometimes used to cut down on spam since it requires an action by a human sender.
Building a Highly-targeted Opt in List: When Money Lies Beneath the Lists
Are you successful with your Internet business? Better yet, do you think you are successful with your online business? When most online entrepreneurs are asked with these questions, they often brush it off.
