Email Bindings

JavaScript/TypeScript native W7S backends can declare Cloudflare Email Service send bindings in w7s.json. W7S uploads those declarations as Worker send_email bindings, so backend code can call env.EMAIL.send(...) without storing an email API token in the repository.

W7S only uploads the runtime binding. The sending domain must already be enabled for Email Service in the Cloudflare account before the backend sends mail.

Declare the binding

Add bindings.email to w7s.json:

w7s.json

{
  "bindings": {
    "email": ["EMAIL"]
  }
}

W7S exposes this binding to the backend at env.EMAIL.

Send an email

backend/index.ts

type Env = {
  EMAIL: {
    send(message: {
      to: string | string[];
      from: string | { email: string; name?: string };
      subject: string;
      text?: string;
      html?: string;
      replyTo?: string;
    }): Promise<{ messageId?: string }>;
  };
};

export default {
  async fetch(_request: Request, env: Env) {
    const result = await env.EMAIL.send({
      to: "customer@example.com",
      from: { email: "noreply@example.com", name: "Example App" },
      subject: "Welcome",
      text: "Thanks for signing up.",
      html: "<p>Thanks for signing up.</p>"
    });

    return Response.json({ sent: true, messageId: result.messageId ?? null });
  }
};

The from address must use a domain that is enabled for Email Service sending. Include both text and html when possible so more email clients can render the message.

Restrict the binding

You can restrict a binding to specific sender or destination addresses:

w7s.json

{
  "bindings": {
    "email": [
      {
        "binding": "EMAIL",
        "allowedSenderAddresses": ["noreply@example.com"],
        "allowedDestinationAddresses": ["ops@example.com"]
      }
    ]
  }
}

W7S also accepts Cloudflare-style snake_case fields:

w7s.json

{
  "bindings": {
    "email": [
      {
        "binding": "EMAIL",
        "allowed_sender_addresses": ["noreply@example.com"],
        "allowed_destination_addresses": ["ops@example.com"]
      }
    ]
  }
}

Use destinationAddress when the binding should send only to one fixed recipient:

w7s.json

{
  "bindings": {
    "email": [
      {
        "binding": "ALERT_EMAIL",
        "destinationAddress": "ops@example.com"
      }
    ]
  }
}

destinationAddress and allowedDestinationAddresses are mutually exclusive.

Limitations

• Email bindings require a JavaScript or TypeScript native backend deployment.
• W7S does not onboard Email Service sending domains.
• W7S currently allows up to two email bindings per app.
• Cloudflare Email Service is intended for transactional email, not bulk marketing sends.