How to Use Resend API for Email: Complete Guide (2026)

How to Use Resend API for Email: Complete Guide (2026)

Resend is a modern email API built for developers who are tired of fighting legacy email infrastructure. Created by the team behind React Email, Resend offers a clean API, excellent deliverability, and first-class support for frameworks like Next.js, Node.js, and Python.

This guide walks you through everything you need to start sending transactional emails with Resend, from account setup to production-ready code examples.

Why Resend?

Before diving in, here is how Resend compares to the alternatives:

Feature	Resend	SendGrid	Amazon SES	Postmark
Free tier	3,000 emails/month	100 emails/day	62,000/month (12 months)	100 emails/month
Pricing starts at	$20/month	$19.95/month	$0.10 per 1,000	$15/month
React Email support	Native	No	No	No
API simplicity	Excellent	Moderate	Complex	Good
Webhook support	Yes	Yes	Yes (via SNS)	Yes
Custom domains	Yes	Yes	Yes	Yes

Resend stands out for its developer experience. The API is minimal, the documentation is excellent, and it integrates natively with React Email for building beautiful templates with JSX.

Prerequisites

Before you start, make sure you have:

• A Resend account (sign up at resend.com)
• A verified domain (or use the sandbox onboarding@resend.dev for testing)
• Node.js 18+ or Python 3.7+ installed
• An API key from the Resend dashboard

Step 1: Get Your API Key

1. Log in to the Resend dashboard at resend.com.
2. Navigate to API Keys in the sidebar.
3. Click Create API Key.
4. Give it a name like "Production" and select the appropriate permissions.
5. Copy the key immediately. It starts with re_ and will not be shown again.

# Store your API key as an environment variable
export RESEND_API_KEY="re_your_api_key_here"

Step 2: Verify Your Domain

To send emails from your own domain instead of the sandbox, you need to verify DNS records.

1. Go to Domains in the Resend dashboard.
2. Click Add Domain and enter your domain (e.g., mail.yourdomain.com).
3. Add the DNS records Resend provides to your domain registrar:

Record Type	Name	Value
TXT	_resend.yourdomain.com	Verification string
MX	bounce.yourdomain.com	Provided by Resend
TXT	bounce.yourdomain.com	SPF record
CNAME	resend._domainkey.yourdomain.com	DKIM record

4. Click Verify once the DNS records have propagated (usually 5-30 minutes).

Step 3: Send Your First Email

Using cURL

The simplest way to test the API:

curl -X POST 'https://api.resend.com/emails' \
  -H 'Authorization: Bearer re_your_api_key_here' \
  -H 'Content-Type: application/json' \
  -d '{
    "from": "You <hello@yourdomain.com>",
    "to": ["recipient@example.com"],
    "subject": "Hello from Resend",
    "html": "<h1>Welcome!</h1><p>Your first email via Resend API.</p>"
  }'

A successful response returns a 200 status with the email ID:

{
  "id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794"
}

Using Node.js

Install the official SDK:

npm install resend

Send an email:

import { Resend } from 'resend';

const resend = new Resend(process.env.RESEND_API_KEY);

async function sendEmail() {
  const { data, error } = await resend.emails.send({
    from: 'You <hello@yourdomain.com>',
    to: ['recipient@example.com'],
    subject: 'Hello from Resend',
    html: '<h1>Welcome!</h1><p>Your first email via Resend.</p>',
  });

  if (error) {
    console.error('Failed to send email:', error);
    return;
  }

  console.log('Email sent:', data.id);
}

sendEmail();

Using Python

Install the Python SDK:

pip install resend

Send an email:

import resend
import os

resend.api_key = os.environ["RESEND_API_KEY"]

params: resend.Emails.SendParams = {
    "from": "You <hello@yourdomain.com>",
    "to": ["recipient@example.com"],
    "subject": "Hello from Resend",
    "html": "<h1>Welcome!</h1><p>Your first email via Resend.</p>",
}

email = resend.Emails.send(params)
print(f"Email sent: {email['id']}")

Step 4: Use React Email Templates

One of Resend's biggest advantages is native React Email support. You can build email templates with JSX components instead of writing raw HTML tables.

Install React Email:

npm install @react-email/components

Create a template:

// emails/welcome.tsx
import { Html, Head, Body, Container, Text, Button } from '@react-email/components';

export default function WelcomeEmail({ name }: { name: string }) {
  return (
    <Html>
      <Head />
      <Body style={{ fontFamily: 'Arial, sans-serif', backgroundColor: '#f4f4f5' }}>
        <Container style={{ maxWidth: '600px', margin: '0 auto', padding: '20px' }}>
          <Text style={{ fontSize: '24px', fontWeight: 'bold' }}>
            Welcome, {name}!
          </Text>
          <Text>
            Thank you for signing up. We are excited to have you on board.
          </Text>
          <Button
            href="https://yourdomain.com/dashboard"
            style={{
              backgroundColor: '#000',
              color: '#fff',
              padding: '12px 24px',
              borderRadius: '6px',
              textDecoration: 'none',
            }}
          >
            Go to Dashboard
          </Button>
        </Container>
      </Body>
    </Html>
  );
}

Send the template with Resend:

import { Resend } from 'resend';
import WelcomeEmail from './emails/welcome';

const resend = new Resend(process.env.RESEND_API_KEY);

await resend.emails.send({
  from: 'You <hello@yourdomain.com>',
  to: ['recipient@example.com'],
  subject: 'Welcome to Our Platform',
  react: WelcomeEmail({ name: 'Alice' }),
});

Step 5: Handle Webhooks

Resend can notify your server about email events like delivery, bounces, and opens.

1. Go to Webhooks in the Resend dashboard.
2. Add your endpoint URL (e.g., https://yourdomain.com/api/webhooks/resend).
3. Select the events you want to receive.

Handle the webhook in your API route:

// app/api/webhooks/resend/route.ts (Next.js App Router)
import { NextRequest, NextResponse } from 'next/server';

export async function POST(req: NextRequest) {
  const body = await req.json();

  switch (body.type) {
    case 'email.delivered':
      console.log(`Email ${body.data.email_id} delivered to ${body.data.to}`);
      break;
    case 'email.bounced':
      console.log(`Email ${body.data.email_id} bounced`);
      // Remove invalid email from your database
      break;
    case 'email.complained':
      console.log(`Spam complaint for ${body.data.email_id}`);
      // Unsubscribe the user
      break;
  }

  return NextResponse.json({ received: true });
}

Common Webhook Events

Event	Description
email.sent	Email accepted by Resend
email.delivered	Email delivered to recipient's mail server
email.bounced	Email bounced (invalid address)
email.complained	Recipient marked as spam
email.opened	Recipient opened the email
email.clicked	Recipient clicked a link

Step 6: Batch Sending

Need to send multiple emails at once? Use the batch endpoint:

const { data, error } = await resend.batch.send([
  {
    from: 'You <hello@yourdomain.com>',
    to: ['user1@example.com'],
    subject: 'Your weekly report',
    html: '<p>Here is your report...</p>',
  },
  {
    from: 'You <hello@yourdomain.com>',
    to: ['user2@example.com'],
    subject: 'Your weekly report',
    html: '<p>Here is your report...</p>',
  },
]);

The batch endpoint supports up to 100 emails per request.

Error Handling Best Practices

Always handle errors gracefully when working with the Resend API:

import { Resend } from 'resend';

const resend = new Resend(process.env.RESEND_API_KEY);

async function sendWithRetry(params, maxRetries = 3) {
  for (let attempt = 1; attempt <= maxRetries; attempt++) {
    const { data, error } = await resend.emails.send(params);

    if (!error) return data;

    if (error.statusCode === 429) {
      // Rate limited - wait and retry
      const delay = Math.pow(2, attempt) * 1000;
      console.log(`Rate limited. Retrying in ${delay}ms...`);
      await new Promise(resolve => setTimeout(resolve, delay));
      continue;
    }

    // Non-retryable error
    throw new Error(`Resend API error: ${error.message}`);
  }

  throw new Error('Max retries exceeded');
}

Rate Limits

Plan	Rate Limit
Free	2 emails/second
Pro	50 emails/second
Enterprise	Custom

Quick Reference: API Endpoints

Endpoint	Method	Description
/emails	POST	Send a single email
/emails/{id}	GET	Retrieve email details
/emails/{id}	PATCH	Update a scheduled email
/emails/batch	POST	Send up to 100 emails
/domains	GET	List verified domains
/domains	POST	Add a new domain
/api-keys	POST	Create an API key

Wrapping Up

Resend makes transactional email simple for developers. The clean API, React Email integration, and generous free tier make it an excellent choice for projects of any size. Start with the sandbox for testing, verify your domain for production, and use webhooks to track delivery.

If you are building applications that need media generation alongside email workflows, such as sending AI-generated images or video thumbnails in your emails, check out Hypereal AI. Hypereal provides simple APIs for AI image generation, video creation, and more that pair perfectly with transactional email pipelines.