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Integrate Lettr into your Node.js application to send transactional emails. Choose the guide that matches your framework. Using Cursor? Jump straight in using this prompt

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Prerequisites

Before you begin, make sure you have:
  1. A Lettr account — sign up at app.lettr.com
  2. An API key created in your dashboard
  3. A verified sending domain
  4. Node.js 18 or higher

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Choose Your Framework

Next.js

Send emails from Next.js API routes and server components

Nuxt

Integrate Lettr with Nuxt server routes

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Direct API Usage

For any Node.js application, you can send emails directly via the REST API using fetch: 
const apiKey = 'lttr_xxxxxxxxxxxx';

const response = await fetch('https://app.lettr.com/api/emails', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${apiKey}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    from: 'you@yourdomain.com',
    to: ['recipient@example.com'],
    subject: 'Hello from Lettr',
    html: '<p>Your email content here.</p>',
  }),
});

const data = await response.json();
console.log(data);
For the full API reference, see the Send Email endpoint.