send0 MCP server

send0

Give any agent an email address in one API call. Open-source email inboxes for AI agents. Send, receive, thread and wait, with webhooks on every plan.

Docs · Quickstart · OpenAPI · Dashboard

Most email APIs are built to send receipts. send0 starts from the inbox: each agent gets a real address that receives, sends and holds threaded conversations, and every message arrives parsed, with the parts an agent needs already pulled out.

import { Send0 } from "@send0/sdk";

const send0 = new Send0(process.env.SEND0_API_KEY);

const inbox = await send0.inboxes.create({ name: "signup-agent" });
// → signup-agent@send0.email

await browser.fill("#email", inbox.address);
await browser.click("Create account");

// Blocks until the email lands, then returns it with the code already extracted.
const msg = await send0.inboxes.wait(inbox.id, { from: "*@github.com", timeout: 60 });
msg?.extracted?.otp; // "482913"

await send0.messages.reply(msg.id, { text: "Thanks, confirmed." }); // threads in Gmail and Outlook

Features

• An address in one call. name@send0.email is ready in milliseconds (custom domains are coming). Plus-addressing (bot+task42@) tags mail without more inboxes.
• Wait, don't poll. One long-poll call blocks until the email you need arrives and returns the one-time code and verification link.
• Clean, structured messages. The new reply text without quoted history, SPF/DKIM/DMARC verdicts, and a prompt-injection flag on every inbound message.
• Real threads. Outbound mail carries Message-ID, In-Reply-To and References, so conversations stay threaded for your agent and for the person on the other side.
• Webhooks and live events on every plan. Signed webhooks (send0-signature, Stripe-style HMAC) with automatic retries and manual redelivery, plus a Server-Sent Events stream.
• Built for agents, safe by default. Inbox-scoped API keys, human approval for outgoing mail, reply-only sending on the free tier, automatic suppression of bounces and complaints, and sending that pauses itself when complaint or bounce rates spike.
• MCP server. Plug inboxes into Claude, Cursor, VS Code or any MCP client, locally or at https://api.send0.dev/mcp.
• Agent framework tools. The same tools for the Vercel AI SDK, LangChain.js and LangChain for Python, with errors returned to the model and optional approval before sending.
• A dashboard for the humans. Read threads, approve drafts, manage keys, webhooks and teammates at app.send0.dev.

Use it

Shortened. The full README is on GitHub.