Email marketing ROI = (revenue - cost) / cost × 100. Industry average is $36-42 per $1 spent — significantly higher than social media ($2-5) or paid search ($2-3). ROI is maximized through list quality, segmentation, personalization, and automation. Calculate ROI by tracking revenue from campaign clicks via UTM parameters and conversion tracking. MisarMail includes revenue attribution tracking to connect email clicks to actual purchases.