In short, email segmentation is when you divide your email subscriber list into smaller groups by using criteria like location, gender, purchase history, and interests to categorize your subscribers. The benefit of using email segmentation is that it helps you to send them personalized emails that they will find more relevant, valuable, and interesting. From the subject line to the content, there are various elements that you can personalize. All things considered, personalization is absolutely key to increasing your open rates.