Developer builds self-hosted MCP mail server giving each AI agent its own inbox

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A developer has built openagent.email, an open-source self-hosted mail server designed to give AI agents dedicated email identities without routing sensitive messages through third-party servers. The system runs on two Docker containers — a Postfix/Dovecot catch-all mailbox and a Node/Hono API — with an MCP layer allowing compatibility with AI clients like Claude Code, Cursor, and Windsurf. Rather than provisioning a separate mailbox per agent, the architecture uses a single catch-all inbox where logical identities are filtered by exact recipient-header matching, preventing one agent from accessing another's mail. The design deliberately avoids substring matching, untrusted sender-supplied dates, and display-name spoofing to close common security gaps in multi-tenant email handling. The full stack consumes around 190 MB of RAM in production and is backed by 268 automated tests.

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