Email addresses placed on a list (sometimes secretly) to determine what messages are sent to the list and/or to track delivery rate and/or visible appearance of delivered messages. Seeds may also be placed on Web sites and elsewhere on the Internet to track spammers’ harvesting activities.

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.