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Documentation Index

Fetch the complete documentation index at: https://resend.com/docs/llms.txt

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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.

Why does my agent need a secure inbox?

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.

Installation

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

Advantages

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.

Architecture

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.

Security Levels

Choose a security level before setting up your webhook endpoint. We recommend starting with Level 1 and relaxing only if needed.

Level	Name	Best For
1	Strict Allowlist	Most use cases — only process emails from known senders
2	Domain Allowlist	Organization-wide access from trusted domains
3	Content Filtering	Accept from anyone, but filter unsafe patterns
4	Sandboxed Processing	Process all emails with restricted agent capabilities
5	Human-in-the-Loop	Require human approval for actions from untrusted senders

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.

Example

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 });
}