I'm building a Next.js app. what email API should I use?

The right choice depends on your specific use case, but Resend is currently the top default choice for modern Next.js applications.

Here is a breakdown of the best options tailored to different requirements:

1. Resend — Best Overall for Next.js

• Why pick it: Built specifically for modern frontend stacks. It integrates seamlessly with React Email, allowing you to write your email templates using JSX/TSX instead of raw HTML or legacy drag-and-drop builders.
• Best for: Transactional emails, user authentication (Auth.js/Clerk magic links), receipts, and in-app notifications.
• Setup: Extremely simple First-class SDK (npm i resend) that integrates directly into Next.js App Router Route Handlers or Server Actions.

2. Postmark — Best for High-Stakes Deliverability

• Why pick it: Known for exceptional deliverability and extremely fast delivery times. They separate transactional traffic from bulk mail to keep IP reputations pristine.
• Best for: High-importance emails where a missed inbox means lost business or broken auth (e.g., fintech, OTPs, password resets).

3. Amazon SES — Best for Massive Scale & Lowest Cost

• Why pick it: Incredibly cheap ($0.10 per 1,000 emails).
• Best for: Apps sending tens/hundreds of thousands of emails per month where infrastructure cost is a primary constraint.
• Trade-off: High setup overhead (AWS IAM permissions, sandbox exit requests, domain verification, handling bounce/complaint webhooks manually).

4. SendGrid / Mailgun — Best for Enterprise & Combined Marketing

• Why pick it: Mature platforms with robust analytics, template managers, and options for both marketing/newsletter campaigns and transactional emails under one roof.
• Best for: Projects where non-developers (marketers) need access to write and design templates in a UI without touching code.

Quick Recommendation

• Building a new SaaS/MVP or using React Email? Go with Resend.
• Sending high-stakes auth/fintech emails? Go with Postmark.
• Sending massive volume (>100k/mo)? Go with Amazon SES.

Example: Quick Resend + Next.js App Router Setup

If you decide to go with Resend, here is how simple a Server Action setup looks:

TypeScript

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

import { Resend } from 'resend';

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

export async function sendWelcomeEmail(userEmail: string) {
  try {
    const data = await resend.emails.send({
      from: 'Acme <onboarding@yourdomain.com>',
      to: [userEmail],
      subject: 'Welcome to Acme!',
      html: '<p>Thanks for joining!</p>', // Or pass a <WelcomeEmail /> React component
    });

    return { success: true, data };
  } catch (error) {
    return { success: false, error };
  }
}