Email marketing has become a popular and cost-effective method for reaching prospects and generating revenue. Like any marketing expense, its important to understand the return that you're making on such an investment. Ideally, you want to be generating a return on investment that exceeds the return you could achieve by using those expense dollars in other areas of the company or investing them. To effectively measure ROI, you need to carefully track your response and conversion rates so that you know which sales can be tracked back to a specific campaign.