email-testing

An email and SMTP testing tool with API for developers

Awesome Opensource Email Resources

Self-hosted inbound email infrastructure with a high-performance C++ SMTP ingestion engine, local storage, and developer APIs.

Mailosaur email and SMS testing commands for Cypress

Self-hosted email testing gateway for developers, CI, and coding agents: capture, inspect, wait for, validate, and route SMTP mail via Web UI, REST, Webhooks, WebSocket, and read-only MCP.

Official Mailtrap MCP server — over 125 tools to send email from Claude, Cursor, VS Code & other AI assistants. Send transactional and bulk email, test in Email Sandbox, manage templates, contacts, domains and webhooks, and inspect delivery logs and stats.

Local SMTP testing made easy

Realistic email testing server in a single Docker container. SMTP, IMAP, DKIM/DMARC, spam filtering, REST API, Node/Python SDKs, and an MCP server.

Self-hostable disposable email with an API your tests can actually use: private inboxes, wait-for-mail, OTP extraction, webhooks.

Mailosaur email and SMS testing library for Node.js

A cross-platform desktop app for catching and viewing emails during development. Built with Laravel, NativePHP & Filament.

The email compatibility engine behind Emailens, as a TypeScript library. Checks HTML, React Email, MJML and Maizzle CSS and HTML against 21 email clients: per-client transforms and scores, dark-mode simulation, suggested fixes, and spam, accessibility, link and image checks. Runs offline. MIT.

The rendering linter for email, in your terminal and CI. HTML, React Email, MJML and Maizzle checked against 21 email clients, with line:column positions and exit codes that fail the build. Runs locally: no account, no network.

A Laravel mail driver that stores outgoing mail in your database, plus a mailbox to read it.

Mailosaur email and SMS testing library for Java

Mailosaur Ruby Client Library

Deutscher Mail-Tester für Nicht-Techniker: SPF, DKIM, DMARC, Sperrlisten und Spam-Score 0 bis 10, mit Klartext-Anleitung für den eigenen Anbieter. Unbegrenzt kostenlos, Server in Deutschland.

Mailosaur email and SMS testing library for Python

MCP server that lets Claude Code, Cursor and other agents check the emails they write: preview, analyze, audit, fix and diff HTML, React Email, MJML and Maizzle across 21 email clients. Local tools run offline; screenshots and share links use emailens.dev.

📫 The Post. A modern mail server & utilities. Ships with a CLI, library, and UI.