Mailpit review: an open-source SMTP testing tool with a web UI and API for capturing and inspecting emails during development. Features, setup, and…
Mailpit is an open-source SMTP testing tool and web-based email viewer built specifically for developers. Instead of sending test emails to real inboxes during development, applications are pointed at Mailpit's built-in SMTP server, which intercepts every message and stores it locally for inspection.
The tool is written in Go and ships as a single, zero-dependency binary alongside official Docker images, which makes it trivial to drop into local development environments, Docker Compose stacks, and continuous integration pipelines. It succeeded older tools like MailHog as the de facto standard for local email capture in many PHP, Laravel, WordPress, and Node.js projects.
At its core, Mailpit provides a modern web dashboard for viewing captured emails, showing the rendered HTML, plain-text version, raw source, headers, and attachments for every message it receives. It also includes an HTML/CSS compatibility checker and a spam-score estimate so developers can catch rendering and deliverability issues before an email ever reaches a real inbox.
Beyond the UI, Mailpit exposes a REST API for automated testing, an optional POP3 server for connecting real mail clients, and webhook notifications that fire whenever a new message arrives. It also supports STARTTLS with custom certificates, letting teams test secure SMTP configurations locally.
Mailpit is completely free and open source; there are no paid tiers, seat limits, or usage caps. Anyone can self-host it on a laptop, a shared development server, or inside a CI pipeline at no cost.
Because there is no subscription model, teams can send unlimited test emails and run full test suites as often as they like without incurring per-email or per-seat charges, which is one of the main reasons it has become popular as a replacement for hosted sandbox services in cost-sensitive workflows.
Mailpit is used by developers to capture and inspect emails sent by applications during development and testing, instead of delivering them to real inboxes.
Yes, Mailpit is free and open source with no paid tiers or usage limits.
No, Mailpit ships as a single self-contained binary or Docker image with no external dependencies required.
Yes, its REST API and lightweight footprint make it well suited for automated integration testing in continuous integration environments.
Mailpit is a modern, actively maintained successor to tools like MailHog, offering a faster interface, lower resource usage, and additional features such as webhooks and spam-score checks.
Yes, Mailpit includes an optional POP3 server that lets real email clients connect and download captured test messages.