When a hotlink is included in an email, a clickthrough occurs when a recipient clicks on the link. clickthrough tracking refers to the data collected about each clickthrough link, such as how many people clicked it, how many clicks resulted in desired actions such as sales, forwards or subscriptions.

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.