curl -X PATCH 'https://api.resend.com/inboxes/inbox-id/threads/thread-id' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0' \
  -H 'Content-Type: application/json' \
  -d '{
  "read": true,
  "folder": "archive"
}'

# PATCH /inboxes/{inbox_id}/threads/{thread_id} (Resend API)
Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-10-20

> Update an existing inbox thread

## Critical Gotchas
* All requests must include a `User-Agent` header (e.g. `User-Agent: my-app/1.0`) or the API returns HTTP 403.

## cURL
curl -X PATCH 'https://api.resend.com/inboxes/inbox-id/threads/thread-id' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0' \
  -H 'Content-Type: application/json' \
  -d '{"read":true,"folder":"archive"}'

## Parameters
| Name | In | Type | Required | Description |
| :--- | :--- | :--- | :--- | :--- |
| inbox_id | path | string | Yes | The Inbox ID or the inbox email address, such as `support... |
| thread_id | path | string | Yes | The Thread ID. |
| read | body | boolean | Yes | Marks every email in the thread read or unread. |
| folder | body | string | No | Moves the thread to this folder. `sent` is assigned autom... |

## Response (200 OK)
{"object":"inbox_thread","id":"4d8e2a1c-9b3f-4c6d-8a21-3e5f7c9c0d12"}

---
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PATCH

PATCH /inboxes/{inbox_id}/threads/{thread_id} — Resend API

Resend API

Update an existing inbox thread

Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-10-20 · upstream hash matched

Actions Try in browser→

Agents: curl -H "Accept: text/markdown" this URL
→ 227 tokens · Vary: Accept

Critical gotchas

All requests must include a User-Agent header (e.g. User-Agent: my-app/1.0) or the API returns HTTP 403.

cURL

curl -X PATCH 'https://api.resend.com/inboxes/inbox-id/threads/thread-id' \  -H "Authorization: Bearer $RESEND_API_KEY" \  -H 'User-Agent: my-app/1.0' \  -H 'Content-Type: application/json' \  -d '{  "read": true,  "folder": "archive"}'

Parameters

Name	In	Type	Required	Description
inbox_id	path	string	Yes	The Inbox ID or the inbox email address, such as `[email protected]`. A value that contains `@` must be a valid email address, and any other value must be a UUID, or the request returns a 422. The address match is case-insensitive and never falls back to the inbox `name`. An address that matches no inbox returns a 404.
thread_id	path	string	Yes	The Thread ID.
read	body	boolean	Yes	Marks every email in the thread read or unread.
folder	body	string	No	Moves the thread to this folder. `sent` is assigned automatically and cannot be set.

Response 200 OK

{
  "object": "inbox_thread",
  "id": "4d8e2a1c-9b3f-4c6d-8a21-3e5f7c9c0d12",
  "subject": "Refund for order 1041",
  "folder": "inbox",
  "labels": [
    {
      "id": "7f9c1d2e-4a6b-4c3d-8e15-9b0a7c6d5e34",
      "name": "Urgent",
      "color": "#E93D82"
    }
  ],
  "read": false
}

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