Resend currently doesn’t manage contact lists for transactional emails. If you manage your own list, you can add the List-Unsubscribe: https://example.com/unsubscribe header when sending emails using the Resend API. As of Febuary 2024, your bulk messages must include a URL version in your list-unsubscribe header, List-Unsubscribe-Post: List-Unsubscribe=One-Click, and to allow for a POST request from the same URL. When receiving a POST, it should return a blank page with 200 (OK) or 202 (Accepted), and should show the regular unsubscribe page with the GET method. Ensure that users stop receiving email within 48 hours of this request. This header allows email clients to offer an easy “Unsubscribe” option in their UI, enhancing user experience and decreasing spam complaints. You can read more about this requirement in our Bulk Sending Requirements blog post.
Node.js
import { Resend } from 'resend';

const resend = new Resend('re_xxxxxxxxx');

await resend.emails.send({
  from: 'Acme <onboarding@resend.dev>',
  to: ['delivered@resend.dev'],
  subject: 'hello world',
  text: 'it works!',
  headers: {
    'List-Unsubscribe': '<https://example.com/unsubscribe>',
  },
});

​
Example

Unsubscribe url header

See the full source code.