Letterhead is the all-in-one ESP for teams that run newsletters like products — everything you need to produce, grow, understand, and monetize every newsletter, in one platform. A powerful drag-and-drop builder with global, lockable templates cuts production time by up to 75%. Audience and content intelligence — powered by billions of sends — shows exactly what's working. Built-in monetization (direct ads, programmatic, house promotions, and conversion CTAs) turns engagement into revenue. Deliverability, audience management, agentic tools, and an API-first design with a native MCP server complete the platform, so your team and your AI agents can curate, segment, and send across your entire portfolio. Teams see +32% engagement within 90 days and +22% revenue on monetized sends. The world's leading newsletter teams — including Condé Nast, WIRED, and Townsquare Media — run on Letterhead.