Email Subject Lines: Engaging subject lines can increase open rates and, consequently, RPE. Target Audience: Tailoring emails to the right audience can significantly boost RPE. Content Quality: High-quality, relevant content can lead to better engagement and higher revenue. Call-to-Action (CTA): Effective CTAs can drive conversions and increase revenue. Timing: Sending emails at optimal times can improve open and click-through rates, enhancing RPE.