Why?
One of the email’s advantages over other communication channels is that it’s a push medium. You send your message, and it gets in front of them. This is a good thing, but it might also be a disadvantage, especially if your email messages are long because they see it, think to themselves “later,” or even worse “delete.”
How?
What if your email messages would become more pull than push. They’ll have only a subject line (the headline), and the body will just be a link. You gain two advantages: 1. They get used to this format from you, so there’s a higher probability they’ll take a look and not think “TLDR.” 2. When they do read it, it’s on your webpage where you can do a lot more than in their email client (precise tracking, pop-ups, etc.)