1. Open Rates: Track how many recipients open your emails. Higher open rates indicate that your subject lines and sender reputation are compelling. 2. Click-Through Rates: Measure the percentage of recipients who click on links within your emails. This shows how engaging your content is. 3. Conversion Rates: Monitor the number of subscribers who take a desired action, such as making a purchase or signing up for an event, after clicking through your email. 4. Subscriber Retention: Assess how well you retain subscribers over time. A high retention rate suggests that your emails are providing ongoing value. 5. Feedback and Surveys: Collect feedback directly from your audience to understand what they find valuable and how you can improve.