Cold email: 50–125 words. That's the range the 2026 outreach studies keep converging on. Replies drop sharply past ~200 words, and sub-50-word notes read as templated. One problem, one line of credibility, one easy ask.
Marketing email to your own list runs longer because trust exists: 150–300 words covers a useful-thing email comfortably. The real limit isn't words, it's ideas. One idea, one link. Emails die of subject sprawl, not length.
The formatting rule that matters more than count: written like one person emailing another. Short paragraphs, no newsletter costume, readable in a phone-screen glance.