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Mailpit
What it is
Mailpit is a free, open-source utility for developers testing email content and SMTP delivery without sending messages to real email addresses. It provides a local SMTP server, a web interface, and an API for integration testing. The interface can display formatted HTML, highlighted source, text, headers, raw messages, and MIME attachments with image thumbnails. Checks include HTML compatibility comparisons, link checking, optional SpamAssassin scoring, and screenshots. The REST API can access, search, delete, send, tag, and release messages; webhooks can send message summaries to external services. Messages can also be relayed, automatically forwarded, tagged, or used to trigger configurable SMTP errors. Mailpit runs as a single binary or a multi-architecture Docker image, with static binaries for Windows, Linux, and Mac. The web UI and API can use HTTPS and basic authentication; SMTP can be configured with authentication and TLS. By default, SMTP listens on port 1025 without encryption or authentication. Mailpit retains the most recent 500 messages by default, and optional POP3 exposes only the latest 100.
For and against
For
- Free and open source.
- Inspects HTML, text, headers, raw messages, and attachments.
- Includes HTML compatibility and link checks.
- REST API supports integration testing.
- Runs as a binary or Docker image.
Against
- Default SMTP listener has no encryption or authentication.
- Retains only the most recent 500 messages by default.
- Optional POP3 exposes only the latest 100 messages.
- Tracking images are still allowed in the UI.
The verdict
Mailpit offers developers local email inspection, automated checks, and integration-testing tools at no cost. Review its default SMTP security settings and retention behavior when planning a setup.
Who it suits
Mailpit suits developers testing email functionality, including in CI/CD pipelines, without sending messages to real addresses. Its local SMTP server and integration-testing API are relevant to teams automating email checks.
Plans and prices
Mailpit
Single static binary or multi-architecture Docker images · Default retention: most recent 500 emails
Read 4 Oct 2026 · mailpit.axllent.org
On the record
- Automated testing
- Mailpit offers a REST API for integration testing and a Chaos feature that can trigger configurable SMTP errors.mailpit.axllent.org · read 4 Oct 2026
- Automation
- Mailpit provides a REST API for accessing, searching, deleting, sending, tagging, and releasing messages.mailpit.axllent.org · read 4 Oct 2026
- Capacity and retention
- Mailpit reports SMTP ingestion of 100–200 emails per second depending on system and message factors, and by default prunes messages to keep the most recent 500.mailpit.axllent.org · read 4 Oct 2026
- Default SMTP configuration
- By default, SMTP listens on port 1025 without encryption or authentication.mailpit.axllent.org · read 4 Oct 2026
- Deployment
- Mailpit runs as a single binary or multi-architecture Docker image, and publishes static binaries for Windows, Linux, and Mac.mailpit.axllent.org · read 4 Oct 2026
- Developer features
- The web UI can show formatted HTML, HTML source, text, headers, raw source, and MIME attachments, including image thumbnails.mailpit.axllent.org · read 4 Oct 2026
- Email checks
- Mailpit offers HTML email compatibility checks, link checks, SpamAssassin-based spam checks, and HTML message screenshots.mailpit.axllent.org · read 4 Oct 2026
- Email rendering security
- The UI applies a strict Content-Security-Policy that blocks remote content other than images, stylesheets, and fonts, and sets a no-referrer policy.mailpit.axllent.org · read 4 Oct 2026
- HTML checks
- HTML Check compares messages against more than 175 HTML and CSS checks based on compatibility data from caniemail.com.mailpit.axllent.org · read 4 Oct 2026
- Install format
- Mailpit runs as a single binary or multi-architecture Docker image without additional dependencies.mailpit.axllent.org · read 4 Oct 2026
- Integrations
- The project says Mailpit is used by projects including Laravel, DDEV, Quarkus, and Saleor, and in CI/CD pipelines.mailpit.axllent.org · read 4 Oct 2026
- Intended audience
- Mailpit is described as a development SMTP and email testing tool for developers, including use in CI/CD pipelines.mailpit.axllent.org · read 4 Oct 2026
- Intended users
- Mailpit is aimed at developers testing email functionality without sending messages to real email addresses.mailpit.axllent.org · read 4 Oct 2026
- Message handling
- Messages can be tagged, relayed through another SMTP server, automatically forwarded, or used to trigger configurable SMTP errors for resilience testing.mailpit.axllent.org · read 4 Oct 2026
- Message inspection
- The web UI can display formatted HTML, highlighted HTML source, text, headers, raw source, and MIME attachments with image thumbnails.mailpit.axllent.org · read 4 Oct 2026
- Network safety
- Link checking blocks requests to internal networks by default to help prevent server-side request forgery.mailpit.axllent.org · read 4 Oct 2026
- Notable limits
- Mailpit keeps the most recent 500 emails by default, and its SMTP server allows up to 100 recipients per message by default.mailpit.axllent.org · read 4 Oct 2026
- Other testing tools
- Features include link checking, HTML message screenshots from the web UI, and optional spam scoring through SpamAssassin.mailpit.axllent.org · read 4 Oct 2026
