Maddy

Composable all-in-one mail server replacing multiple daemons

Maestro

Scalable workflow orchestrator powering Netflix’s data platform

Magda

Federated data catalog with scalable search and Kubernetes‑native deployment

Mage OSS

Build modern data pipelines locally with visual, modular code

magic-trace

High‑resolution, low‑overhead tracing of every function call

MailCatcher

Capture and view outgoing email locally via a simple web UI

MailCrab

Lightweight Rust‑based email sandbox with web UI and API

MailDev

Local SMTP server for testing emails during development

MailHog

Lightweight email testing tool with web UI and API

Mail-in-a-Box

One-click, self-hosted email server that just works

Mailpit

Fast, zero-dependency email testing tool for developers

Mailtrain

Self-hosted newsletter platform with advanced automation and segmentation

Mailu

Fully featured Docker‑based mail server that's simple to deploy

Manba

Unified HTTP API gateway with traffic control and plugins

Manticore Search

Fast open-source database built for high-performance search

MapServer

Powerful CGI engine for creating web‑based GIS maps and services

Mara Pipelines

Lightweight Python ETL framework with PostgreSQL and web UI

marimo

Reactive Python notebooks that stay reproducible, git‑friendly, and deployable

Marquez

Centralized metadata service for data lineage and lifecycle

Mastodon

Self‑hosted, federated microblogging platform powered by ActivityPub

Mastra

TypeScript framework for building scalable AI agents and workflows

Matano

Serverless security data lake for AWS with detection-as-code

Materialize

Real-time SQL platform delivering up-to-the-second data views

Mathesar

Spreadsheet interface for PostgreSQL databases, self-hosted and collaborative