Lettr Node.js SDK

Official Node.js SDK for the Lettr transactional email API. Type-safe client that returns a Result ({ data, error }) instead of throwing — covers emails, templates, domains, webhooks, audience, and campaigns.

Installation

npm install lettr
# or: pnpm add lettr / yarn add lettr / bun add lettr

Usage

import { Lettr } from "lettr";

const client = new Lettr(process.env.LETTR_API_KEY!);

const { data, error } = await client.emails.send({
  from: "[email protected]",
  to: ["[email protected]"],
  subject: "Welcome!",
  html: "<p>Hello!</p>",
});

if (error) {
  // error.type is "validation" | "api" | "network"
  console.error(error.message);
} else {
  console.log(data.request_id);
}

Every method returns a Result<T> — destructure { data, error } and handle error before reading data. The SDK never throws for API or network failures.

Documentation

Full guides for every resource, with complete request/response details, live in the docs:

📚 docs.lettr.com/quickstart/nodejs

| Topic | Guide | |-|-| | Install, client, the Result pattern | Installation | | HTML, text, templates, attachments, scheduling, errors | Sending Emails | | Manage Lettr templates & merge tags | Templates | | Add, verify, and manage sending domains | Domains | | Webhook endpoints for delivery & engagement events | Webhooks | | Lists, contacts, topics, properties, segments | Audience | | List, send, and schedule campaigns | Campaigns | | Endpoint reference (params & schemas) | API Reference |

License

MIT