Should I use HTML or plain text-based emails? And how long should my emails be?

This is another example of A/B testing in action. Even though some individuals swear by the beautiful, eye-catching pictures of HTML emails, others believe that basic text appears best in any email software and is never blocked as an image may be, there is no one perfect solution. Again, it all depends on your target audience and their tastes, so experiment with both and see which one works best.

Use this as a guideline: the typical individual will spend around 20 seconds reading an email. If your email will take more than 20 seconds to read, make sure the most important content, as well as your call to action and links, are at the top, where they can be seen without scrolling.