Email A/B testing is the process of testing two variations of an email to determine which performs better. Marketers experiment with subject lines, email copy, images, CTAs, and send times to improve engagement. CRMs and email marketing platforms like Mailchimp and HubSpot provide built-in A/B testing tools. Key metrics analyzed include open rates, click-through rates, and conversion rates. A/B testing helps businesses refine their messaging, increase campaign effectiveness, and maximize ROI. By continuously testing and optimizing, companies ensure they deliver the most compelling email content to their audience.