# Reply to Thread Email

::::callout{intent="warning"}
Inboxes are currently in private beta and only available to a limited
number of users. The response shape might change before GA.

[Get early access](https://resend.com/help?type=report\&message=I+would+like+early+access+to+Inboxes.\&priority=low) if you're interested in testing this feature.

Once you have access, upgrade your Resend SDK to use the new methods:

:::code-group
```bash Node.js
npm install resend@6.28.1-preview-inboxes.2
```

```bash CLI
npm install -g resend-cli@2.22.0-preview-inboxes.2
```
:::
::::

Replies from the inbox address. Recipients are taken from the message you
reply to.

At least one of `html` or `text` is required.

## Path Parameters

The Inbox ID.

The Thread ID.

The Email ID of the message to reply to, as returned in the thread's
`messages[].id`.

## Body Parameters

- `html` (string) — The HTML body.

- `text` (string) — The plain-text body.

- `subject` (string) — The subject of the reply. When omitted, the thread subject is used, prefixed with `Re:` if it isn't already.

## Response Fields

- `id` (string) — The ID of the queued outbound email.

- `email_id` (string) — The ID of the queued outbound email. Same value as `id`.

- `direction` (string) — Always `outbound`.

- `from` (string) — Sender email address.

- `to` (string\[]) — The recipients of the message.

- `cc` (string\[]) — The CC recipients of the message.

- `bcc` (string\[]) — The BCC recipients of the message.

- `reply_to` (string\[]) — Always an empty array.

- `subject` (string) — The subject of the sent reply.

- `message_id` (string | null) — Always `null`.

- `html` (string | null) — The HTML body.

- `text` (string | null) — The plain-text body.

- `attachments` (array) — The attachments on the message.

  :::accordion{title="properties"}
  - `id` (string) — The ID of the attachment.

  - `filename` (string | null) — The filename of the attachment.

  - `size` (number | null) — The size of the attachment in bytes.
  :::

- `read` (boolean) — Whether the message has been read.

- `received_at` (string) — ISO 8601 timestamp when the message was sent.

:::code-group
```ts Node.js
import { Resend } from 'resend';

const resend = new Resend('re_xxxxxxxxx');

const { data, error } = await resend.inboxes.threads.emails.reply({
  inboxId: 'b3e2b2b6-3f0e-4c8e-9ad3-2f43a1e2c7f1',
  threadId: '4d8e2a1c-9b3f-4c6d-8a21-3e5f7c9c0d12',
  emailId: '5b1a9f47-2c8d-4e6f-9a03-1d2e3f4a5b60',
  html: '<p>Refund issued for order 1041.</p>',
  text: 'Refund issued for order 1041.',
});
```

```bash cURL
curl -X POST 'https://api.resend.com/inboxes/b3e2b2b6-3f0e-4c8e-9ad3-2f43a1e2c7f1/threads/4d8e2a1c-9b3f-4c6d-8a21-3e5f7c9c0d12/emails/5b1a9f47-2c8d-4e6f-9a03-1d2e3f4a5b60/reply' \
     -H 'Authorization: Bearer re_xxxxxxxxx' \
     -H 'Content-Type: application/json' \
     -d $'{
  "html": "<p>Refund issued for order 1041.</p>",
  "text": "Refund issued for order 1041."
}'
```

```bash CLI
resend inboxes threads emails reply \
  --inbox_id b3e2b2b6-3f0e-4c8e-9ad3-2f43a1e2c7f1 \
  --thread_id 4d8e2a1c-9b3f-4c6d-8a21-3e5f7c9c0d12 \
  --email_id 5b1a9f47-2c8d-4e6f-9a03-1d2e3f4a5b60 \
  --html "<p>Refund issued for order 1041.</p>" \
  --text "Refund issued for order 1041."
```
:::

:::code-group
```json Response
{
  "id": "6a0c8e58-3d9e-4f7a-8b14-2e3f4a5b6c71",
  "email_id": "6a0c8e58-3d9e-4f7a-8b14-2e3f4a5b6c71",
  "direction": "outbound",
  "from": "support@example.com",
  "to": ["Ada Lovelace <ada@example.org>"],
  "cc": [],
  "bcc": [],
  "reply_to": [],
  "subject": "Re: Refund for order 1041",
  "message_id": null,
  "html": "<p>Refund issued for order 1041.</p>",
  "text": "Refund issued for order 1041.",
  "attachments": [],
  "read": true,
  "received_at": "2026-08-05T14:12:04.110Z"
}
```
:::

## Related pages

- [Account Management](./account-management-index.md)
- [API Keys](./api-keys-2-index.md)
- [API Keys](./api-keys-index.md)
- [API Reference](./api-reference-index.md)
- [AudiencesDEPRECATED](./audiencesdeprecated-index.md)
- [Authorized Apps](./authorized-apps-index.md)
- [Automations](./automations-index.md)
- [Broadcasts](./broadcasts-index.md)
- [Build with AI](./build-with-ai-index.md)
- [Changelog](../changelog.md)

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