A process that requires new list joiners to take an action (such as clicking on an emailed link to a personal confirmation page) in order to confirm that they do want to be on the list. Sometimes interpreted incorrectly by some email broadcast vendors to mean a new subscriber who does not opt-out of or bounce a welcome message.

3 Quick And Easy Ways To Build A Profitable Opt-In List
You finally realize that you need a good opt-in list. After reading countless articles and sought expert advices and have read many success stories of people creating a small fortune with opt-in lists you finally decide to have one of your own.