1. Surveys: Send out short surveys to your email list asking specific questions about what they liked or disliked about the email. 2. A/B Testing: Conduct A/B tests to compare different elements of your emails, such as subject lines, images, or CTAs, and gather data on what performs better. 3. Engagement Metrics: Analyze open rates, click-through rates, and conversion rates to understand what resonates with your audience. 4. Direct Responses: Encourage recipients to reply directly to your emails with their feedback.