Lightweight local SMTP written in Typescript for automated testing, including integrations for various testing frameworks - prominently Playwright.

It captures incoming email in memory and gives you simple helpers to:

• wait for a message
• read a mailbox by recipient
• clear mail state between tests
• assert verification email flows

Why this exists

• End-to-end tests often need real email behavior without external providers.
• smtp-for-testing runs locally, accepts incoming mail, parses it, and stores it per recipient so your tests can assert real delivery behaviour.

Tech stack and relevant libraries

smtp-server: receives SMTP messages locally mailparser: parses raw message streams into structured mail objects nodemailer: useful for sending test messages into the local SMTP server

Install npm install smtp-for-testing

Quick start

import { MailServer } from "smtp-for-testing";

const mailServer = new MailServer(2525);

await mailServer.start();

// run your app action that sends email...

const mail = await mailServer.waitForMail("[email protected]", 3000);
console.log(mail.subject);

await mailServer.stop();

License ISC