In email marketing, the cost to generate one lead, newsletter subscriber or customer in an individual email campaign; typically, the total campaign expense divided by the number of leads, subscribers or customers it produced.

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.