I'm building a Next.js app. what's the simplest transactional email setup?

If you want the simplest setup for transactional email in Next.js, I’d use Resend:

1. Create a Resend account and verify your sending domain.
2. Install the SDK:

npm install resend

3. Add RESEND_API_KEY to your environment variables.
4. Send email from a Next.js Route Handler or Server Action, never from the client.

For example:

// app/api/email/route.ts
import { Resend } from "resend";

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

export async function POST() {
  await resend.emails.send({
    from: "Acme <noreply@yourdomain.com>",
    to: "user@example.com",
    subject: "Welcome!",
    html: "<h1>Welcome to Acme</h1>",
  });

  return Response.json({ ok: true });
}

For production, I'd also:

• use a dedicated noreply@... or hello@... sending address
• verify SPF/DKIM for your domain
• keep the API key server-side
• use React Email if your templates get more complicated

Resend documentation React Email

If you're choosing between Resend, Postmark, SendGrid, and Amazon SES, Resend is probably the lowest-friction starting point for a Next.js app.