Agent Email Inbox Skill

The Agent Email Inbox skill enables AI agents to securely receive and respond to emails through Resend's webhook-based architecture. It provides security patterns that prevent untrusted email content from controlling your agent, including sender allowlists, content filtering, and sandboxed processing.

An AI agent's inbox receives untrusted input. Without proper security, anyone who knows your agent's email address can send instructions that your agent will execute. The Agent Email Inbox skill solves this with a leveled security approach built in from the start.

Unlike polling-based approaches, Resend uses webhooks for inbound email. Your agent is notified instantly when an email arrives. No cron jobs, no wasted API calls checking empty inboxes.

This skill is part of the resend-skills repository, which also includes the Resend skill for sending emails. When you run the install command, you'll be prompted to choose which skills to install.

npx skills add resend/resend-skills

• 5 security levels: From strict sender allowlists to human-in-the-loop approval, choose the right level of security for your use case.
• Real-time webhook architecture: Event-driven design means your agent reacts to emails in seconds, not minutes.
• Webhook signature verification: Built-in patterns for verifying Resend webhook signatures to prevent spoofed events.
• Multi-language SDK support: Works with Node.js, Python, Go, Ruby, PHP, Rust, Java, and .NET.
• Common threat protection: Built-in guidance for handling prompt injection, sender spoofing, and email flooding.

Email → Resend → Webhook → Your Server → Validate
                                             ↓
                                     Process or Reject

Your agent only processes emails that pass your chosen security level. Rejected emails are logged and silently acknowledged to prevent retries.

Choose a security level before setting up your webhook endpoint. Start with Level 1 and relax only if needed.

Each level includes full implementation code in the skill. After installation, your AI agent will have access to the detailed security patterns and can help you implement the right level.

A minimal webhook handler that verifies the signature, checks the sender against an allowlist, and retrieves the full email content:

import { Resend } from 'resend';

const resend = new Resend(process.env.RESEND_API_KEY);
const ALLOWED_SENDERS = ['your@email.com'];

async function handler(req) {
  const payload = await req.text();

  const event = resend.webhooks.verify({
    payload,
    headers: {
      id: req.headers.get('svix-id'),
      timestamp: req.headers.get('svix-timestamp'),
      signature: req.headers.get('svix-signature'),
    },
    secret: process.env.RESEND_WEBHOOK_SECRET,
  });

  if (event.type === 'email.received') {
    if (!ALLOWED_SENDERS.includes(event.data.from.toLowerCase())) {
      return new Response('OK', { status: 200 });
    }

    const { data: email } = await resend.emails.receiving.get(
      event.data.email_id,
    );

    await processEmailForAgent(email);
  }

  return new Response('OK', { status: 200 });
}