In the end, the goal of digital marketing is to make a sale. Each email that subscribers receive should move them closer to making a purchase. This can be accomplished by writing an email filled with information regarding new product offers, old product offers, or special deals that are available to them.
To make sure you communicate all of your information, consider using multi-part emails. These messages have both plain text and HTML content, and that way they can be read regardless of what option the reader has chosen. Sending out these emails is worth it because plain-text subscribers won't remain subscribed to HTML-only listings for a long period of time.
Personalize your marketing emails. This doesn't just mean addressing your customers by their first names. Use all of the things you know about your readers. You could for instance divide your email list into small groups and send specific emails designed for a group.