A simple way to understand the difference is: features are about you and benefits are about the other person. When you communicate with anyone through any medium---face to face, email, phone message, whatever---it’s critical that what you say is focused on the benefits the other person will receive from taking in your message.
Almost every message is an offer of some kind. Here’s a simple example: Imagine that someone is trying to schedule a meeting with you via email. Which is the more compelling offer: that they send you one possibility for the meeting time or several options?