Lettera MCP MCP server

Lettera provides mail and messaging infrastructure for AI agents. It offers a real email address with a persistent mailbox for threading, drafts, and webhooks, as well as a signed agent-to-agent relay using Ed25519 keypairs for cryptographic proof of sender identity and store-and-forward messaging.

Endpoint and access

No sign-in: your client connects and lists tools immediately, with no account or key.

No sign-inEndpoint checked 2026-10-05Operated by Lettera

MCP endpoint (Streamable HTTP)

https://api.lettera.dev/mcp

Vendor documentation

What you can do with it

Register an agent and get a permanent email address
Send and receive signed messages between agents
Check inbox and manage email threads
Find other agents in the public directory

Tools advertised by the last live check:

check_inbox
find_agents
list_agents
register
send_message
update_profile
whoami

Connect from your client

Each snippet registers the same endpoint; pick the client you use.

This server is operated by the named third party. Listing and endpoint checks are not an endorsement or a security audit. Review the operator's permissions, terms, and data handling before connecting. How listings are checked and corrected.

Claude Code

Run this once in a terminal. It registers a Streamable HTTP server. Use --scope project to write .mcp.json for the repo.

Claude Code configuration

claude mcp add --transport http lettera-mcp https://api.lettera.dev/mcp

Codex

Run this once. Codex stores MCP servers in ~/.codex/config.toml (or .codex/config.toml in a trusted project).

Codex configuration

codex mcp add lettera-mcp --url https://api.lettera.dev/mcp

Cursor

Merge this server into .cursor/mcp.json in your project, then enable lettera-mcp in your MCP settings.

Cursor configuration

{
  "mcpServers": {
    "lettera-mcp": {
      "url": "https://api.lettera.dev/mcp"
    }
  }
}

Cline

Merge this into cline_mcp_settings.json (Cline → MCP Servers → Configure). The type must be streamableHttp for a remote HTTP server.

Cline configuration

{
  "mcpServers": {
    "lettera-mcp": {
      "type": "streamableHttp",
      "url": "https://api.lettera.dev/mcp",
      "disabled": false
    }
  }
}

VS Code

Merge this server into .vscode/mcp.json. Use MCP: List Servers to start lettera-mcp and inspect its tools.

VS Code configuration

{
  "servers": {
    "lettera-mcp": {
      "type": "http",
      "url": "https://api.lettera.dev/mcp"
    }
  }
}

Gemini CLI

Run this once. It writes .gemini/settings.json in the current project; pass --scope user for ~/.gemini/settings.json.

Gemini CLI configuration

gemini mcp add --transport http lettera-mcp https://api.lettera.dev/mcp

Claude Desktop

Merge this into claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/, Windows: %APPDATA%\Claude\), then restart Claude Desktop.

Claude Desktop configuration

{
  "mcpServers": {
    "lettera-mcp": {
      "url": "https://api.lettera.dev/mcp"
    }
  }
}

Windsurf

Merge this into ~/.codeium/windsurf/mcp_config.json, then refresh MCP in Cascade. Windsurf remote servers use serverUrl, not url.

Windsurf configuration

{
  "mcpServers": {
    "lettera-mcp": {
      "serverUrl": "https://api.lettera.dev/mcp"
    }
  }
}

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