---
title: Resend
description: Bidirectional email adapter for Chat SDK. Receive emails via Resend webhooks and send rich HTML emails via the Resend API.
tagline: Email adapter for Chat SDK powered by Resend. Receive inbound emails via webhooks, send rich HTML replies, and proactively start email threads with `openDM`.
package: @resend/chat-sdk-adapter
---

# Resend



## Install

<PackageInstall package="@resend/chat-sdk-adapter chat @chat-adapter/shared" />

## Quick start

```typescript title="lib/bot.ts" lineNumbers
import { Chat } from "chat";
import { createMemoryState } from "@chat-adapter/state-memory";
import { createResendAdapter } from "@resend/chat-sdk-adapter";

const resend = createResendAdapter({
  fromAddress: "bot@yourdomain.com",
  fromName: "My Bot", // optional
  // apiKey: "re_...",            // or set RESEND_API_KEY
  // webhookSecret: "whsec_...",  // or set RESEND_WEBHOOK_SECRET
});

const chat = new Chat({
  userName: "email-bot",
  adapters: { resend },
  state: createMemoryState(),
});

// New inbound email starts a new thread.
chat.onNewMention(async (thread, message) => {
  await thread.subscribe();
  await thread.post(`Got your email: ${message.text}`);
});

// Follow-up email in a subscribed thread.
chat.onSubscribedMessage(async (thread, message) => {
  await thread.post(`Reply: ${message.text}`);
});
```

Forward Resend webhooks to your server's webhook endpoint. The adapter verifies signatures and routes events into the Chat SDK handler pipeline. See the [`examples/basic`](https://github.com/resend/resend-chat-sdk/tree/main/examples/basic) folder in the adapter repo for a full working server.

## Configuration

<TypeTable
  type={{
  fromAddress: {
    type: "string",
    description: "Sender email address. Required.",
  },
  fromName: {
    type: "string",
    description: "Display name used in the From header.",
  },
  apiKey: {
    type: "string",
    description:
      "Resend API key. Auto-detected from `RESEND_API_KEY` when omitted.",
  },
  webhookSecret: {
    type: "string",
    description:
      "Webhook signing secret. Auto-detected from `RESEND_WEBHOOK_SECRET` when omitted.",
  },
}}
/>

### Environment variables

| Variable                | Required                       | Description                                                                 |
| ----------------------- | ------------------------------ | --------------------------------------------------------------------------- |
| `RESEND_API_KEY`        | Yes, unless `apiKey` is passed | Resend API key. Overridden by `config.apiKey`.                              |
| `RESEND_WEBHOOK_SECRET` | For webhooks                   | Webhook signing secret. Overridden by `config.webhookSecret`.               |
| `FROM_ADDRESS`          | No                             | Used by example apps only. The adapter takes the sender from `fromAddress`. |

## Email threading

Threads are resolved using the standard `Message-ID`, `In-Reply-To`, and `References` email headers. Reply chains are grouped into Chat SDK threads automatically, and your handlers receive each follow-up as an `onSubscribedMessage` event on the same thread.

## Sending email proactively

Use `openDM` to start a new email thread to any address, for example to send notifications, alerts, or scheduled reports:

```typescript
const threadId = await chat.adapters.resend.openDM("user@example.com");
const thread = await chat.thread("resend", threadId);
await thread.post("Hello from the bot!");
```

## Rich card emails

Post a Chat SDK [card](/docs/cards) and the adapter renders it to HTML email through [`@react-email/components`](https://react.email/):

```typescript
await thread.post({
  card: {
    type: "card",
    title: "Order Confirmed",
    children: [
      { type: "text", content: "Your order #1234 has been shipped." },
      { type: "divider" },
      {
        type: "link-button",
        label: "Track Order",
        url: "https://example.com/track/1234",
      },
    ],
  },
  fallbackText: "Order #1234 confirmed",
});
```

## Attachments

Inbound email attachments are exposed on `message.raw.attachments` as objects with `filename`, `content_type`, and `url` fields, not on `message.attachments`. Your handler can fetch the URL or pass it on to downstream processing.

The adapter doesn't send attachments. Files included in a posted message are not attached to the outgoing email.

## Limitations

Email has no native concept of message edits, reactions, or typing indicators, so these operations throw `NotImplementedError`:

* `editMessage` / `deleteMessage`
* `addReaction` / `removeReaction`
* `startTyping`

Send cards or new replies instead.

## Feature support

<FeatureSupport />

## Resources

Official docs are at [resend.com/docs/chat-sdk](https://resend.com/docs/chat-sdk). Example apps in the adapter repo:

| Example                                                                                     | Description                                      |
| ------------------------------------------------------------------------------------------- | ------------------------------------------------ |
| [basic](https://github.com/resend/resend-chat-sdk/tree/main/examples/basic)                 | Echo bot that replies to every email             |
| [welcome-cards](https://github.com/resend/resend-chat-sdk/tree/main/examples/welcome-cards) | Sends a styled card email on first contact       |
| [notifications](https://github.com/resend/resend-chat-sdk/tree/main/examples/notifications) | Proactive emails via `openDM()` and an HTTP POST |
| [support-bot](https://github.com/resend/resend-chat-sdk/tree/main/examples/support-bot)     | Multi-turn support with subscribe/unsubscribe    |
| [attachments](https://github.com/resend/resend-chat-sdk/tree/main/examples/attachments)     | Detects attachments and replies with a summary   |