A/B testing is a game-changer for email marketing in 2025. It involves comparing two versions of an email to see which performs better. The most common elements tested are subject lines, but you can also test content, images, CTAs, and send times. Start by selecting a single variable to test. For example, you might compare two subject lines with different tones—one formal, one casual. Send each version to a small subset of your list. Based on the open or click rates, you can determine the winner and send that version to the rest of your audience. This process isn’t just for one-off campaigns. You can integrate testing into your automation flows to continuously refine content over time. Be sure your sample size is statistically significant to ensure reliable results. Testing different times of day or days of the week can also reveal when your audience is most engaged. Some might respond better in the morning, others late at night. Test, analyze, adapt—that’s the core philosophy. A/B testing eliminates guesswork and allows you to make data-driven decisions. When done right, it improves engagement, boosts conversions, and helps you understand your audience like never before.