How to send email from Supabase Edge Functions

You can send email from Supabase Edge Functions by creating a Deno-based function that calls a transactional email API (like Resend, Sequenzy, or SendGrid). The function runs server-side, keeps your API key secure, and can be triggered by HTTP requests, database changes, or auth events.

🛠 Step-by-Step Setup

Create a new Edge Function

bash

supabase functions new send-email

This generates supabase/functions/send-email/index.ts.

Store API key securely

bash

supabase secrets set RESEND_API_KEY=re_your_api_key_here

Keys are stored in Supabase secrets, not in code.

Write the function

Example using Resend:

ts

const RESEND_API_KEY = Deno.env.get("RESEND_API_KEY");

Deno.serve(async (req) => {

if (req.method !== "POST") {

• return new Response("Method not allowed", { status: 405 });

}

const { to, subject, body } = await req.json();

const response = await fetch("https://api.resend.com/emails", {

• method: "POST",
• headers: {
• "Content-Type": "application/json",
• Authorization: Bearer ${RESEND_API_KEY},

},

• body: JSON.stringify({
• from: "noreply@yourdomain.com",

to,

subject,

• html: body,

}),

});

return new Response(await response.text(), { status: response.status });

});

Test locally

bash

supabase start

supabase functions serve send-email --env-file .env.local

Then trigger with:

bash

curl -X POST http://localhost:54321/functions/v1/send-email \

• -H "apikey: <SUPABASE_SECRET_KEY>"
  -d '{"to":"user@example.com","subject":"Hello","body":"<strong>It works!</strong>"}'

Deploy to Supabase

bash

supabase functions deploy send-email --no-verify-jwt

Make sure your API key is set in Supabase secrets before deploying.

⚠️ Best Practices

Use SPF/DKIM/DMARC for your sending domain to avoid spam folders.

Keep tokens short-lived if sending auth links.

Log errors and monitor bounce/complaint rates.

Trigger functions from auth hooks or database events for automation.

✅ Recommended Providers

Resend → Developer-friendly, simple transactional emails.

Sequenzy → SaaS-focused, supports sequences and automations.

SendGrid → Enterprise-grade, high-volume support.