Mailbox - Local SMTP

Email testing for developers

Only for Mac

Free · In‑App Purchases

Mac

See every email your app sends — right on your Mac. Local SMTP testing with HTML preview, compatibility checks, mock provider APIs, and webhook simulation. Mailbox is a local email testing tool for developers. Run an SMTP server on your Mac, see every email your app sends, and inspect it instantly — no Docker, no cloud services, no configuration. Point your app at localhost, hit send, and the email appears in Mailbox. That's it. FREE — EVERYTHING YOU NEED TO GET STARTED • 1 local SMTP server on any port • Instant email capture and inspection • Full HTML rendering with dark mode • Mobile preview: see your email in a simulated iPhone viewport • HTML compatibility check: 300+ CSS and HTML features scored across 22 email clients (powered by caniemail.com data) • Headers inspector and raw source view • Attachment preview and download • Search and export as .eml MAILBOX PRO — THE FULL TOOLKIT • Unlimited SMTP servers: run backend, frontend, and staging side by side • Drop-in API replacement: point your SendGrid, Postmark, Brevo, Mailgun, Mailtrap, or Resend integration at a local endpoint. Keep your existing code and API keys — no provider account needed • Webhook simulation: receive delivery, open, and click events locally, in each platform's exact payload format • Email forwarding to a real SMTP server • REST API: query captured emails programmatically for test assertions and CI pipelines • Priority support Pro is available as a monthly or yearly subscription (with a 7-day free trial) or a one-time lifetime purchase. BUILT FOR YOUR WORKFLOW Lives in your menu bar. Auto-starts your servers at launch. Shares servers across your local network. Works with Node.js, Python, PHP, Ruby, Laravel, and anything else that speaks SMTP. 100% native for Apple Silicon. Your emails never leave your Mac. Privacy Policy: https://themailbox.app/privacy Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

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The developer, Danut Florian, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

    Privacy practices may vary, for example, based on the features you use or your age. Learn More

    Accessibility

    The developer has not yet indicated which accessibility features this app supports. Learn More

    Information

    Seller
    Danut Florian
    Size
    6.9 MB
    Category
    Developer Tools
    Compatibility
    Requires macOS 26.0 or later.
    • Mac
      Requires macOS 26.0 or later.
    Languages
    English and 3 more
    • English, French, German, Spanish
    Age Rating
    4+
    In-App Purchases
    Yes
    • Mailbox Pro Yearly $29.99
    • Mailbox Pro Monthly $4.99
    • Mailbox Pro Lifetime $49.99
    • Learn More
    Copyright
    © 2026 Danut Florian
  • Developer Website
  • Privacy Policy