"Messenger" matching MCP servers:

Provides programmatic access to Sidemail.io's transactional email, contacts, domains, and Messenger features via Model Context Protocol (MCP) in VS Code and other MCP clients.

Proof of control for AI agents, through the proof.holdings API: verify domains, phone numbers and messenger accounts, ask a human to approve an action, and issue and verify Proofs of Delegation.

Enables coding-agent sessions to post and collect durable letters through a fully local, SQLite-backed post office, with delivery retried across restarts until the recipient acknowledges. Any MCP client or shell-capable agent can use it to send, read, acknowledge, and review the history of messages between sessions.