Mailcannon is the first open-source cold email outreach platform built entirely on the Model Context Protocol (MCP). It lets Claude, Cursor, and any MCP client manage contacts, create multi-step campaign sequences, send emails through Gmail or Zoho, and track opens/bounces/replies — all through natural language. Unlike Instantly or Lemlist, Mailcannon has no monthly subscription. It's self-hosted, uses MCP as its API layer, and connects to your own email providers.