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Introduction

Learn what Mailloop is and how it helps you test emails during development.

3 min read

Mailloop is an SMTP sandbox that captures emails your application sends and lets you inspect them instantly. Point your SMTP configuration at Mailloop, send emails as normal, and see every message in a web dashboard or through the API.

No emails ever leave the sandbox. It is safe for development, staging, and CI environments.

How It Works

  1. Create a sandbox in the Mailloop dashboard
  2. Point your SMTP config at sandbox.mailloop.io using the sandbox credentials
  3. Send emails as normal from your application
  4. Inspect the results in the dashboard or via the API

Every captured email is available within seconds. You can view the rendered HTML, plain text, headers, and attachments.

What You Can Do

  • Capture and preview emails -- see the rendered HTML side by side with plain text, inspect headers, and download attachments
  • Desktop and mobile preview -- toggle between desktop and mobile viewports to check responsive email layouts
  • Test from any language -- Mailloop is a standard SMTP server. If your language can send email, it works with Mailloop
  • Receive emails from external sources -- sandboxes accept inbound email from any SMTP sender, not just your application
  • Automate email testing -- use the TypeScript SDK to create sandboxes, wait for emails, and assert on content in CI/CD pipelines

Use Cases

Development

Replace your real email provider with Mailloop during development. Preview every email your application sends without worrying about accidentally emailing real users.

QA and Staging

Give your QA team a shared sandbox to verify email content, formatting, and recipient logic before releases.

CI/CD

Create temporary sandboxes in your test suite, trigger your application to send email, and programmatically verify the email arrived with the correct content. Temporary sandboxes auto-delete after your tests finish.

External Email Testing

Receive emails from third-party services (payment processors, notification providers, webhooks-to-email) into a sandbox for inspection and testing.

Key Concepts

Sandboxes

A sandbox is an isolated email testing environment with its own SMTP credentials and inbox. You can create as many sandboxes as your plan allows. Each sandbox has a username, password, and a dedicated email address.

Email Addresses

Every sandbox has a catch-all email address in the format [email protected]. When you authenticate with a sandbox's SMTP credentials, all outgoing emails are captured regardless of the recipient address in the To field.

You can also receive inbound email from external sources by sending to the sandbox address directly.

Next Steps