Mailpit
Open SourceSMTP testing tool for developers with modern web UI and API
AI Summary
Mailpit is a lightweight email testing tool that acts as an SMTP server and displays received test emails in a modern web interface. It offers a REST API for automated testing, HTML compatibility checking, spam testing and requires no additional dependencies.
✓ Pros
- + No dependencies, runs as a single binary or Docker container with minimal resource consumption
- + Extensive features like HTML checker, spam testing, screenshots and POP3 server
- + REST API enables full automation and integration into CI/CD pipelines
✗ Cons
- − Only suitable for test and development environments, not for production emails
- − Advanced features like spam testing require external tools such as SpamAssassin
Use Cases
- → Testing email functionality in local development environments without actual email delivery
- → Automated integration tests for email workflows via the REST API
- → Checking HTML/CSS compatibility of emails with common email clients
- → Spam testing and link validation of marketing and transactional emails
Who is it for?
Developers and QA teams who want to test email functionality locally and integrate automated email tests into their CI/CD pipelines.
Tags
What is Mailpit?
Mailpit is an SMTP test server for local development environments. It intercepts outgoing emails instead of actually sending them, and displays them in a web interface. The tool runs as a single binary with no external dependencies, or alternatively as a Docker container. Resource usage is low. Anyone implementing email sending in an application can use it to test the entire workflow without needing a real mail server and without accidentally sending emails to real recipients.
Core features
- SMTP server with web UI: Mailpit accepts emails via SMTP and displays them immediately in the browser interface, including headers, plain-text and HTML views.
- REST API: All actions can be controlled via an API, enabling integration into automated test suites and CI/CD pipelines.
- HTML compatibility check: The built-in HTML checker shows which CSS and HTML constructs are problematic in which email clients.
- Spam testing: Combined with SpamAssassin, emails can be checked for spam score. SpamAssassin must be installed separately.
- POP3 server: Mailpit also makes received emails available via POP3, which simplifies connecting other tools.
- Link validation: Embedded links in emails can be checked directly for reachability.
Who is Mailpit for?
Developers implementing email features in web applications who want to test locally. Also QA teams looking to cover email workflows in automated tests. The REST API makes Mailpit particularly useful when emails need to be verified as part of integration tests, for example whether a registration email was actually triggered and carries the expected content.
Mailpit is not a production mail server. There is no outbound delivery logic and no configuration for real sending.
Context & alternatives
Mailpit belongs to the category of local SMTP fake servers, a type of tool that is widely used in web development. Well-known alternatives include MailHog (the direct predecessor, now unmaintained) and Mailtrap as a hosted option with a similar feature set. Compared to MailHog, Mailpit offers active development, more features and a more modern interface. Anyone already using MailHog who depends on extended features such as the HTML checker or screenshots has a clear reason to migrate to Mailpit.
