How to Give Your AI Agent Its Own Email Inbox

AI agents can write code, browse the web, and execute multi-step workflows — but most still can't receive a simple email. That's a significant gap. Email is how the world communicates, and an agent without an inbox can't participate in conversations that start there.

AgentSend solves this. It's email infrastructure built specifically for agents: provision a real inbox programmatically, receive messages via webhook, reply using the REST API, and attach files. No SMTP configuration, no human sign-up, no MX record wrestling.

This guide shows you exactly how to do it in under 5 minutes.

What You'll Build

By the end of this guide your agent will have:

• A real email address (e.g. my-agent@agentsend.io or your own domain)
• A webhook endpoint that fires when mail arrives
• The ability to send reply emails programmatically
• A message thread view for full conversation context

Step 1: Create an Account and Get an API Key

Step 2: Create an Inbox

An inbox is the container for your agent's email address. Create one with a single API call:

# Create an inbox for your agent
curl -X POST https://agentsend.io/inboxes \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "my-research-agent",
    "webhookUrl": "https://your-agent-host.com/webhooks/email"
  }'

{
  "id": "inbox_abc123",
  "name": "my-research-agent",
  "address": "my-research-agent@agentsend.io",
  "webhookUrl": "https://your-agent-host.com/webhooks/email",
  "status": "active",
  "createdAt": "2026-03-20T12:00:00Z"
}

Your agent's email address is now live: my-research-agent@agentsend.io.

Step 3: Handle Incoming Email via Webhook

When someone sends an email to your agent's address, AgentSend makes an HTTP POST to your webhookUrl with the full message payload:

{
  "event": "message.received",
  "inboxId": "inbox_abc123",
  "message": {
    "id": "msg_xyz789",
    "threadId": "thread_001",
    "from": "user@example.com",
    "subject": "Can you research this for me?",
    "text": "Hi agent, please look into...",
    "html": "<p>Hi agent, please look into...</p>",
    "attachments": [],
    "receivedAt": "2026-03-20T12:01:00Z"
  }
}

Here's a minimal webhook handler in Node.js that feeds the email directly into an AI agent:

import Anthropic from "@anthropic-ai/sdk";
import AgentSend from "@agentsend/sdk";

const claude = new Anthropic();
const agentSend = new AgentSend({ apiKey: process.env.AGENTSEND_API_KEY });

export async function handleEmailWebhook(payload) {
  const { message } = payload;

  // Ask Claude to respond
  const response = await claude.messages.create({
    model: "claude-sonnet-4-6",
    max_tokens: 1024,
    messages: [{
      role: "user",
      content: `Email from ${message.from}:\n\n${message.text}`
    }]
  });

  // Reply via AgentSend
  await agentSend.messages.send({
    inboxId: payload.inboxId,
    threadId: message.threadId,
    to: message.from,
    subject: `Re: ${message.subject}`,
    text: response.content[0].text
  });
}

Step 4: Send Emails Proactively

Your agent doesn't have to wait for incoming mail. It can initiate conversations:

curl -X POST https://agentsend.io/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "inboxId": "inbox_abc123",
    "to": "recipient@example.com",
    "subject": "Research report ready",
    "text": "Hi, I have completed the research you requested...",
    "html": "<p>Hi, I have completed the research...</p>"
  }'

Step 5: Use the MCP Skill (Claude Agents)

If your agent runs on Claude, the fastest path is the AgentSend MCP skill. Install it once and Claude gets native tools to send mail, check inboxes, and read threads — no webhook boilerplate required.

{
  "mcpServers": {
    "agentsend": {
      "command": "npx",
      "args": ["-y", "@agentsend/mcp-skill"],
      "env": {
        "AGENTSEND_API_KEY": "YOUR_API_KEY"
      }
    }
  }
}

Once installed, Claude can call tools like send_email, list_messages, and create_inbox directly — just describe what you want in natural language.

Architecture Tips

One inbox per agent, not per user

Design around agent identity. Each distinct agent role (research agent, scheduling agent, customer support agent) should have its own inbox. This keeps threads clean and makes conversation routing trivial.

Use threads for conversation context

AgentSend groups related messages into threads automatically. When your agent replies, include the threadId from the webhook payload to stay in the same thread. Fetch the full thread with GET /threads/{threadId}/messages to give your agent conversation history.

Idempotency for webhook reliability

Webhooks may be delivered more than once. Use the message.id field to deduplicate — store processed IDs in a cache or database and skip re-processing if already seen.

Test with bounce rate monitoring

AgentSend automatically pauses an inbox if its bounce rate exceeds 5% or complaint rate exceeds 0.1%. Validate recipient addresses before sending to keep your sender reputation healthy.