Email marketing is a perfect way to increase your annual revenue per customer by upselling and reselling your customers. Update them on exciting company announcements, creative product use ideas, and promotions that they won't want to miss. Even if the email doesn't create immediate conversions, it keeps you and your business at the top of their mind and, when it comes time to make a purchase decision, they'll turn to you. On the other hand, sometimes a well-timed email is exactly what you need to push a customer from "waiting" to "buying."