Several elements in an email can be tested to optimize performance:
1. Subject Lines: Test different subject lines to see which one gets the higher open rate. 2. Call to Action (CTA): Experiment with different CTA texts, colors, and placements to see what drives more clicks. 3. Email Copy: Test different lengths, tones, and formats of your email content. 4. Images: Experiment with different images, including their size, placement, and relevance. 5. Sending Time: Test different days and times to find out when your audience is most likely to engage.