Write for one specific reader, not your full list
The most-read newsletters sound like they were written for one person. Before writing each issue, picture your ideal subscriber — their situation, what they are trying to accomplish, and what would genuinely help them this week. Write to that person. When a subscriber reads your newsletter and thinks "this was written for exactly where I am right now," you have achieved the highest form of email engagement. The paradox is that the more specifically you write for one person, the more universally resonant the writing becomes.