A specific, pro-active, request by an individual email recipient to have their own email address placed on a specific mailing list. Many list renters and buyers now require list owners to provide proof of opt-in, including the actual email or IP address date and time the request was received.

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.