How to Send Transactional Email with Bun and TypeScript (Zero Dependencies)

Why legacy email libraries feel sluggish in Bun

Bun has revolutionized JavaScript backends by delivering sub-millisecond cold starts, native TypeScript execution, and high-performance I/O. Yet most email tutorials still instruct developers to install `nodemailer` alongside dozens of legacy stream polyfills.

In modern cloud environments, transactional email should be dispatched over HTTP/2 with native `fetch` and zero external dependencies.

Method 1: Sending via Bun Native Fetch (Zero Dependencies)

Because Bun has native `fetch` with connection pooling, you can dispatch authenticated emails in four lines of code without installing any packages:

// send.ts — run directly with `bun send.ts`
const response = await fetch('https://api.sadasend.com/v1/emails', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${process.env.SADASEND_API_KEY}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    from: 'system@yourdomain.com',
    to: 'user@example.com',
    subject: 'Your authentication code',
    text: 'Your code is: 482-910. Valid for 10 minutes.',
  }),
});

const data = await response.json();
console.log('Dispatched message ID:', data.id);

Method 2: Using the Type-Safe SadaSend SDK

For complex applications, use the lightweight `@sadasend/sdk` package for complete autocomplete, payload validation, and automatic retries:

import { SadaSend } from '@sadasend/sdk';

const sadasend = new SadaSend({ apiKey: process.env.SADASEND_API_KEY });

const result = await sadasend.emails.send({
  from: 'notifications@yourdomain.com',
  to: 'founder@startup.io',
  subject: 'Weekly Infrastructure Report',
  markdown: `
# Weekly Summary
All systems operational.
- **Uptime:** 99.99%
- **Delivery Latency:** 412ms
  `,
});

Microtask Queue Dispatching in Bun

In high-throughput API handlers (such as user signup routes), you never want to block the HTTP response on an external email network request. Use Bun's microtask scheduling:

// In your Bun.serve() route handler:
queueMicrotask(async () => {
  try {
    await sadasend.emails.send({ ...payload });
  } catch (err) {
    console.error('Background send failed:', err);
  }
});

return new Response(JSON.stringify({ status: 'user_created' }), { status: 201 });