Resend

Modern email API for developers with React Email support.

Quick Start

Install:

npm install resend

Environment variable:

# .env.local
RESEND_API_KEY=re_...

Basic Usage

Send Simple Email

import { Resend } from 'resend';

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

const { data, error } = await resend.emails.send({
  from: 'Acme <noreply@acme.com>',
  to: ['user@example.com'],
  subject: 'Hello World',
  html: '<p>Welcome to our app!</p>',
});

API Route (Next.js App Router)

// app/api/send/route.ts
import { Resend } from 'resend';
import { NextResponse } from 'next/server';

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

export async function POST(req: Request) {
  const { to, subject, message } = await req.json();

  try {
    const { data, error } = await resend.emails.send({
      from: 'Acme <noreply@acme.com>',
      to: [to],
      subject,
      html: `<p>${message}</p>`,
    });

    if (error) {
      return NextResponse.json({ error }, { status: 400 });
    }

    return NextResponse.json({ data });
  } catch (error) {
    return NextResponse.json(
      { error: 'Failed to send email' },
      { status: 500 }
    );
  }
}

React Email Templates

Install React Email

npm install @react-email/components

Create Template

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

interface WelcomeEmailProps {
  username: string;
  loginUrl: string;
}

export function WelcomeEmail({ username, loginUrl }: WelcomeEmailProps) {
  return (
    <Html>
      <Head />
      <Preview>Welcome to Acme - Your account is ready!</Preview>
      <Body style={main}>
        <Container style={container}>
          <Img
            src="https://acme.com/logo.png"
            width={48}
            height={48}
            alt="Acme"
          />
          <Heading style={h1}>Welcome, {username}!</Heading>
          <Text style={text}>
            Thanks for signing up for Acme. We're excited to have you on board.
          </Text>
          <Section style={buttonContainer}>
            <Button style={button} href={loginUrl}>
              Get Started
            </Button>
          </Section>
          <Text style={footer}>
            If you didn't create an account, you can safely ignore this email.
          </Text>
        </Container>
      </Body>
    </Html>
  );
}

const main = {
  backgroundColor: '#f6f9fc',
  fontFamily:
    '-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Ubuntu,sans-serif',
};

const container = {
  backgroundColor: '#ffffff',
  margin: '0 auto',
  padding: '40px 20px',
  borderRadius: '5px',
  maxWidth: '465px',
};

const h1 = {
  color: '#1f2937',
  fontSize: '24px',
  fontWeight: '600',
  lineHeight: '40px',
  margin: '0 0 20px',
};

const text = {
  color: '#4b5563',
  fontSize: '14px',
  lineHeight: '24px',
  margin: '0 0 20px',
};

const buttonContainer = {
  textAlign: 'center' as const,
  margin: '30px 0',
};

const button = {
  backgroundColor: '#3b82f6',
  borderRadius: '5px',
  color: '#fff',
  fontSize: '14px',
  fontWeight: '600',
  textDecoration: 'none',
  textAlign: 'center' as const,
  display: 'inline-block',
  padding: '12px 30px',
};

const footer = {
  color: '#9ca3af',
  fontSize: '12px',
  lineHeight: '16px',
  margin: '20px 0 0',
};

export default WelcomeEmail;

Send with Template

// app/api/send-welcome/route.ts
import { Resend } from 'resend';
import { WelcomeEmail } from '@/emails/welcome';
import { NextResponse } from 'next/server';

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

export async function POST(req: Request) {
  const { email, username } = await req.json();

  try {
    const { data, error } = await resend.emails.send({
      from: 'Acme <noreply@acme.com>',
      to: [email],
      subject: 'Welcome to Acme!',
      react: WelcomeEmail({
        username,
        loginUrl: `${process.env.NEXT_PUBLIC_APP_URL}/login`,
      }),
    });

    if (error) {
      return NextResponse.json({ error }, { status: 400 });
    }

    return NextResponse.json({ data });
  } catch (error) {
    return NextResponse.json(
      { error: 'Failed to send email' },
      { status: 500 }
    );
  }
}

Common Email Templates

Password Reset

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

interface PasswordResetProps {
  resetUrl: string;
  expiresIn: string;
}

export function PasswordResetEmail({ resetUrl, expiresIn }: PasswordResetProps) {
  return (
    <Html>
      <Head />
      <Preview>Reset your password</Preview>
      <Body style={main}>
        <Container style={container}>
          <Heading style={h1}>Reset Your Password</Heading>
          <Text style={text}>
            We received a request to reset your password. Click the button below
            to create a new password.
          </Text>
          <Button style={button} href={resetUrl}>
            Reset Password
          </Button>
          <Text style={text}>
            This link will expire in {expiresIn}. If you didn't request a
            password reset, you can safely ignore this email.
          </Text>
        </Container>
      </Body>
    </Html>
  );
}

Order Confirmation

// emails/order-confirmation.tsx
import {
  Body,
  Column,
  Container,
  Head,
  Heading,
  Hr,
  Html,
  Preview,
  Row,
  Section,
  Text,
} from '@react-email/components';

interface OrderItem {
  name: string;
  quantity: number;
  price: number;
}

interface OrderConfirmationProps {
  orderNumber: string;
  items: OrderItem[];
  total: number;
  shippingAddress: string;
}

export function OrderConfirmationEmail({
  orderNumber,
  items,
  total,
  shippingAddress,
}: OrderConfirmationProps) {
  return (
    <Html>
      <Head />
      <Preview>Order {orderNumber} confirmed</Preview>
      <Body style={main}>
        <Container style={container}>
          <Heading style={h1}>Order Confirmed</Heading>
          <Text style={text}>
            Thanks for your order! Your order number is{' '}
            <strong>{orderNumber}</strong>.
          </Text>

          <Section style={orderSection}>
            <Heading as="h2" style={h2}>
              Order Summary
            </Heading>
            {items.map((item, index) => (
              <Row key={index} style={itemRow}>
                <Column>
                  <Text style={itemName}>{item.name}</Text>
                  <Text style={itemQuantity}>Qty: {item.quantity}</Text>
                </Column>
                <Column style={priceColumn}>
                  <Text style={itemPrice}>${item.price.toFixed(2)}</Text>
                </Column>
              </Row>
            ))}
            <Hr style={hr} />
            <Row>
              <Column>
                <Text style={totalLabel}>Total</Text>
              </Column>
              <Column style={priceColumn}>
                <Text style={totalPrice}>${total.toFixed(2)}</Text>
              </Column>
            </Row>
          </Section>

          <Section>
            <Heading as="h2" style={h2}>
              Shipping Address
            </Heading>
            <Text style={text}>{shippingAddress}</Text>
          </Section>
        </Container>
      </Body>
    </Html>
  );
}

Email Options

Full Options

const { data, error } = await resend.emails.send({
  // Required
  from: 'Acme <noreply@acme.com>',
  to: ['user@example.com'],
  subject: 'Hello',

  // Content (one of these)
  html: '<p>Hello</p>',
  text: 'Hello',
  react: EmailTemplate({ props }),

  // Optional
  cc: ['cc@example.com'],
  bcc: ['bcc@example.com'],
  replyTo: 'support@acme.com',
  headers: {
    'X-Custom-Header': 'value',
  },
  attachments: [
    {
      filename: 'invoice.pdf',
      content: Buffer.from(pdfContent),
    },
  ],
  tags: [
    { name: 'category', value: 'transactional' },
  ],
});

Multiple Recipients

// To multiple addresses
await resend.emails.send({
  from: 'Acme <noreply@acme.com>',
  to: ['user1@example.com', 'user2@example.com'],
  subject: 'Team Update',
  html: '<p>Hello team!</p>',
});

// Batch send (different emails)
const { data, error } = await resend.batch.send([
  {
    from: 'Acme <noreply@acme.com>',
    to: ['user1@example.com'],
    subject: 'Welcome User 1',
    html: '<p>Hello User 1!</p>',
  },
  {
    from: 'Acme <noreply@acme.com>',
    to: ['user2@example.com'],
    subject: 'Welcome User 2',
    html: '<p>Hello User 2!</p>',
  },
]);

Attachments

import { readFileSync } from 'fs';

// From file
const attachment = readFileSync('./invoice.pdf');

await resend.emails.send({
  from: 'Acme <noreply@acme.com>',
  to: ['user@example.com'],
  subject: 'Your Invoice',
  html: '<p>Please find your invoice attached.</p>',
  attachments: [
    {
      filename: 'invoice.pdf',
      content: attachment,
    },
  ],
});

// From URL
await resend.emails.send({
  from: 'Acme <noreply@acme.com>',
  to: ['user@example.com'],
  subject: 'Your Report',
  html: '<p>Please find your report attached.</p>',
  attachments: [
    {
      filename: 'report.pdf',
      path: 'https://example.com/reports/report.pdf',
    },
  ],
});

Preview Emails

Development Server

npm install react-email -D

{
  "scripts": {
    "email": "email dev --dir emails"
  }
}

npm run email

Opens at http://localhost:3000 to preview templates.

Server Actions

// app/actions/email.ts
'use server';

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

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

export async function sendWelcomeEmail(email: string, username: string) {
  try {
    const { data, error } = await resend.emails.send({
      from: 'Acme <noreply@acme.com>',
      to: [email],
      subject: 'Welcome to Acme!',
      react: WelcomeEmail({ username, loginUrl: '/login' }),
    });

    if (error) {
      return { success: false, error: error.message };
    }

    return { success: true, messageId: data?.id };
  } catch (error) {
    return { success: false, error: 'Failed to send email' };
  }
}

Webhooks

// app/api/webhooks/resend/route.ts
import { NextResponse } from 'next/server';

export async function POST(req: Request) {
  const payload = await req.json();

  switch (payload.type) {
    case 'email.sent':
      console.log('Email sent:', payload.data.email_id);
      break;
    case 'email.delivered':
      console.log('Email delivered:', payload.data.email_id);
      break;
    case 'email.bounced':
      console.log('Email bounced:', payload.data.email_id);
      // Handle bounce - update user record
      break;
    case 'email.complained':
      console.log('Spam complaint:', payload.data.email_id);
      // Handle complaint - unsubscribe user
      break;
  }

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

Best Practices

Use React Email - Type-safe, reusable templates
Verify domain - Better deliverability
Handle errors - Check for error response
Use batch for bulk - More efficient
Preview before sending - Use email dev server

Common Mistakes

Mistake	Fix
Unverified domain	Verify in Resend dashboard
Missing from address	Use verified domain email
Not handling errors	Check error response
Inline styles missing	Use style objects in React Email
Large attachments	Keep under 40MB

Reference Files

references/templates.md - More template examples
references/webhooks.md - Webhook events
references/domains.md - Domain verification

resend

Resend

Quick Start

Basic Usage

Send Simple Email

API Route (Next.js App Router)

React Email Templates

Install React Email

Create Template

Send with Template

Common Email Templates

Password Reset

Order Confirmation

Email Options

Full Options

Multiple Recipients

Attachments

Preview Emails

Development Server

Server Actions

Webhooks

Best Practices

Common Mistakes

Reference Files

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