To optimize emails for direct revenue, consider the following tips: 1. Mobile Optimization: Ensure your emails are mobile-friendly as a significant portion of users access emails on their smartphones. 2. Clear Value Proposition: Clearly communicate the benefits and value of the product or service you are promoting. 3. Urgency and Scarcity: Utilizing urgency (limited-time offers) and scarcity (limited stock) can drive immediate action. 4. Re-engagement Campaigns: Target inactive subscribers with re-engagement campaigns to rekindle their interest and drive sales.