agent-email-inbox

AI Agent Email Inbox

Overview

This skill covers setting up a secure email inbox that allows your application or AI agent to receive and respond to emails, with content safety measures in place.

Core principle: An AI agent's inbox receives untrusted input. Security configuration is important to handle this safely.

Why Webhook-Based Receiving?

Resend uses webhooks for inbound email, meaning your agent is notified instantly when an email arrives. This is valuable for agents because:

• Real-time responsiveness — React to emails within seconds, not minutes
• No polling overhead — No cron jobs checking "any new mail?" repeatedly
• Event-driven architecture — Your agent only wakes up when there's actually something to process
• Lower API costs — No wasted calls checking empty inboxes

Architecture

Sender → Email → Resend (MX) → Webhook → Your Server → AI Agent
                                              ↓
                                    Security Validation
                                              ↓
                                    Process or Reject

SDK Version Requirements

This skill requires Resend SDK features for webhook verification (webhooks.verify()) and email receiving (emails.receiving.get()). Always install the latest SDK version. If the project already has a Resend SDK installed, check the version and upgrade if needed.

Language	Package	Min Version
Node.js	resend	>= 6.9.2
Python	resend	>= 2.21.0
Go	resend-go/v3	>= 3.1.0
Ruby	resend	>= 1.0.0
PHP	resend/resend-php	>= 1.1.0
Rust	resend-rs	>= 0.20.0
Java	resend-java	>= 4.11.0
.NET	Resend	>= 0.2.1

Install the resend npm package: npm install resend (or the equivalent for your language). For full sending docs, install the resend skill.

Quick Start

1. Ask the user for their email address — You need a real email address to send test emails to. Ask the user and wait for their response before proceeding.
2. Choose your security level — Decide how to validate incoming emails before any are processed
3. Set up receiving domain — Configure MX records for the user's custom domain (see Domain Setup section)
4. Create webhook endpoint — Handle email.received events with security built in from the start. The webhook endpoint MUST be a POST route.
5. Set up tunneling (local dev) — Use Tailscale Funnel (recommended) or ngrok. See references/webhook-setup.md
6. Create webhook via API — Use the Resend Webhook API to register your endpoint programmatically. See references/webhook-setup.md
7. Connect to agent — Pass validated emails to your AI agent for processing