Test email sending locally

Test email sending functionality locally using wrangler dev to simulate email delivery and verify your sending logic before deploying.

1. Sign up for a Cloudflare account ↗︎.
2. Install Node.js ↗︎.

Configure your Wrangler file with the email binding:

{
	"name": "email-sending-worker",
	// Set this to today's date
	"compatibility_date": "2026-10-15",
	"send_email": [{ "name": "EMAIL" }],
}

name = "email-sending-worker"
# Set this to today's date
compatibility_date = "2026-10-15"

[[send_email]]
name = "EMAIL"

Use remote bindings to develop with Email Service locally. With remote bindings, your Worker runs locally but sends real emails through Email Service.

By default, wrangler dev simulates the email binding locally. It logs emails to the console but does not send them.

Set remote: true on the email binding in your Wrangler configuration:

{
	"name": "email-sending-worker",
	// Set this to today's date
	"compatibility_date": "2026-10-15",
	"send_email": [
		{
			"name": "EMAIL",
			"remote": true,
		},
	],
}

name = "email-sending-worker"
# Set this to today's date
compatibility_date = "2026-10-15"

[[send_email]]
name = "EMAIL"
remote = true

Then run wrangler dev as usual. Calls to env.EMAIL.send() send actual emails through Email Service while your Worker code runs locally.

When running wrangler dev without remote bindings, the email binding is simulated locally. Emails are not sent. Instead, the email content is logged to the console and saved to local files for inspection.

export default {
	async fetch(request, env, ctx) {
		if (request.method !== "POST") {
			return new Response("Method not allowed", { status: 405 });
		}

		try {
			const emailData = await request.json();

			console.log("Sending email:", {
				to: emailData.to,
				from: emailData.from,
				subject: emailData.subject,
			});

			const response = await env.EMAIL.send(emailData);

			return new Response(
				JSON.stringify({
					success: true,
					id: response.messageId,
				}),
				{
					headers: { "Content-Type": "application/json" },
				},
			);
		} catch (error) {
			return new Response(
				JSON.stringify({
					success: false,
					error: error.message,
				}),
				{
					status: 500,
					headers: { "Content-Type": "application/json" },
				},
			);
		}
	},
};

Start your development server:

npx wrangler dev

Send a test email:

curl -X POST http://localhost:8787/ \
  -H "Content-Type: application/json" \
  -d '{
    "to": "recipient@example.com",
    "from": "sender@yourdomain.com",
    "subject": "Test Email",
    "html": "<h1>Hello from Wrangler!</h1>",
    "text": "Hello from Wrangler!"
  }'

Wrangler shows output like:

[wrangler:info] send_email binding called with MessageBuilder:
From: sender@yourdomain.com
To: recipient@example.com
Subject: Test Email

Text: /tmp/miniflare-.../files/email-text/<message-id>.txt

The email content (text and HTML) is saved to local files that you can inspect to verify your email structure before deploying.

Local development simulates the send_email binding locally, but ArrayBuffer values in attachment content cannot be serialized by the local simulator. If you pass an ArrayBuffer (for example, for image or PDF attachments), you receive an error like:

Cannot serialize value: [object ArrayBuffer]

Workaround: Use string content for text-based attachments during local development. To test binary attachments (images, PDFs), deploy your Worker with npx wrangler deploy and test against the deployed version.

This limitation only affects local development — ArrayBuffer content works correctly on deployed Workers.

• Deploy your sending worker: Send emails get started
• Explore advanced patterns: Email sending examples