docs: add REST API availability and subdomain support

- Remove 'Workers binding only' and 'top-level domain required' limitations
- Add REST API page with endpoint, auth, and curl example
- Link to REST API reference across index, get-started, and API pages
- Subdomains are now supported (removed top-level domain restriction)

Author: thomasgauvin

src/content/docs/email-service/api/send-emails/index.mdx

@@ -2,7 +2,7 @@
 title: Send emails
 pcx_content_type: navigation
 summary: |
-  API reference for sending emails with Cloudflare Email Service using Workers API.
+  API reference for sending emails with Cloudflare Email Service using the Workers API or REST API.
 sidebar:
   order: 1
   group:

src/content/docs/email-service/api/send-emails/rest-api.mdx

@@ -0,0 +1,44 @@
+---
+title: REST API
+pcx_content_type: concept
+sidebar:
+  order: 2
+---
+
+The REST API allows you to send emails from any application using standard HTTP requests. This is useful for applications that are not built on Cloudflare Workers or when you need to send emails from external services.
+
+## Endpoint
+
+Send an email using the [Email Sending REST API](https://developers.cloudflare.com/api/resources/email_sending/methods/send).
+
+```txt
+POST https://api.cloudflare.com/client/v4/accounts/{account_id}/email-service/send
+```
+
+## Authentication
+
+Authenticate using a Cloudflare API token with the appropriate permissions. Include the token in the `Authorization` header:
+
+```txt
+Authorization: Bearer <API_TOKEN>
+```
+
+## Example
+
+```bash
+curl "https://api.cloudflare.com/client/v4/accounts/{account_id}/email-service/send" \
+  --header "Authorization: Bearer <API_TOKEN>" \
+  --header "Content-Type: application/json" \
+  --data '{
+    "to": "recipient@example.com",
+    "from": "sender@yourdomain.com",
+    "subject": "Hello from Email Service",
+    "html": "<h1>Hello!</h1><p>This email was sent using the REST API.</p>",
+    "text": "Hello! This email was sent using the REST API."
+  }'
+```
+
+## Next steps
+
+- Refer to the [REST API reference](https://developers.cloudflare.com/api/resources/email_sending/methods/send) for full request and response schemas.
+- See the [Workers API](/email-service/api/send-emails/workers-api/) for sending emails directly from Cloudflare Workers.

src/content/docs/email-service/get-started/send-emails.mdx

@@ -17,7 +17,7 @@ import {
 } from "~/components";
 import DomainSetup from "~/content/partials/email-service/_domain-setup-sending.mdx";
 
-Send emails from your applications using Cloudflare Email Service with the Workers API.
+Send emails from your applications using Cloudflare Email Service with the Workers API or the [REST API](https://developers.cloudflare.com/api/resources/email_sending/methods/send).
 
 :::note
 You must be using Cloudflare DNS to use Email Service.

src/content/docs/email-service/index.mdx

@@ -32,9 +32,7 @@ Cloudflare Email Service is currently in private beta. Access is limited to appr
 **Known limitations:**
 
 - Your domain must use Cloudflare DNS
-- You must use the Workers binding (REST API is not available)
 - Email templates are not available
-- You must onboard the top-level domain to use Email Sending and/or Email Routing
 
 Many of these will be addressed over the course of the private and public beta.
 :::
@@ -52,7 +50,7 @@ Together, these two features make it possible for you to send and receive emails
 - Custom email addresses (support@, contact@, orders@)
 - Emails as a mode of interaction for agents, such as send an email to create an issue in ticket tracking
 
-Access Email Service from Cloudflare Workers using Workers Bindings:
+Access Email Service from Cloudflare Workers using Workers Bindings or via the [REST API](https://developers.cloudflare.com/api/resources/email_sending/methods/send):
 
 <Tabs>
 <TabItem label="index.ts">
@@ -147,7 +145,7 @@ See the full [Workers Email API reference](/email-service/api/send-emails/worker
 </Feature>
 
 <Feature header="Workers API" href="/email-service/api/">
-	Send and route emails using the native Workers API.
+	Send and route emails using the native Workers API or the [REST API](https://developers.cloudflare.com/api/resources/email_sending/methods/send).
 </Feature>
 
 ---