Best open-source alternatives to Gmail

Mailu is an open-source mail server project packaged as a collection of Docker images. It is intended for people who want a full-featured email stack that is straightforward to deploy and maintain without proprietary components or unrelated groupware features. The README highlights support for standard mail protocols such as IMAP, SMTP, and Submission, along with webmail access and an administration interface. It also describes user- and admin-oriented capabilities including aliases, auto-reply, per-domain delegation, quotas, enforced TLS, DKIM, DMARC/SPF, and anti-virus/anti-spam protections.

mailcow is a dockerized mail server project aimed at people and organizations that want to self-host and manage email infrastructure. The README presents it as a packaged suite built around open-source components, with the main entry point for setup and support being the official documentation site. The project emphasizes deployment in containers and a community/support ecosystem rather than describing end-user mail features in detail on the README itself. It also notes that mailcow itself is released under GPLv3, and points readers to support contracts and a one-time SAL for paid assistance from the maintainers.

Docker Mailserver is a containerized mail server aimed at people who want a production-ready email stack without the complexity of a traditional application server. It packages common mail components such as Postfix and Dovecot together with spam filtering, antivirus scanning, DKIM/DMARC handling, and related tooling in a single self-hosted deployment. The project emphasizes simple, versioned configuration using only files rather than a SQL database, which makes it easier to deploy, upgrade, and manage over time. It also provides extensive documentation and a setup script to help with initial configuration and ongoing maintenance. Authentication options include LDAP and OAuth2-based SASL mechanisms, making it suitable for environments that need centralized account integration.

Stalwart is an open-source mail and collaboration server aimed at organizations that need a secure, scalable platform for email and groupware. It combines traditional mail protocols with collaboration features, making it suitable for teams that want a self-hosted alternative for messaging, calendaring, contacts, and file sharing. The project supports a broad set of protocols including IMAP, JMAP, POP3, SMTP, CalDAV, CardDAV, and WebDAV. It also emphasizes operational features such as multi-tenancy, authentication and authorization controls, filtering for spam and phishing, observability, high availability, and web-based administration. The README presents it as a Rust-based server designed for reliability and growth from small deployments to large clusters.

Roundcube Webmail is a self-hosted webmail client intended for users who want a browser-based email experience backed by an IMAP server. It presents itself as an application-like interface and includes common email client capabilities such as MIME handling, address book management, folder operations, search, and spell checking. The project is written primarily in PHP and JavaScript and depends on a database backend such as MariaDB, MySQL, PostgreSQL, or SQLite, plus external libraries. It is designed to run on a webserver and can be extended through a plugin API, while the user interface can be customized with skins. The README also points users to separate installation and upgrade documentation for deployment guidance.

Mail-in-a-Box is a self-hosted email appliance designed to make running a personal mail server simple. It turns a fresh Ubuntu 22.04 LTS 64-bit machine into a configured stack for receiving, sending, and managing email, with a focus on privacy, decentralization, and low-effort deployment. The project bundles the major mail-server components needed for a complete setup, including SMTP, IMAP, webmail, spam filtering, DNS, TLS certificates, backups, and monitoring. It also provides a control panel for managing users, aliases, DNS records, and backups, plus an API for control-panel actions. The README positions it for individuals who want to self-host email without dealing with a highly customizable or manually assembled server environment.

Mox is a self-hosted mail server aimed at people and organizations that want to run their own email infrastructure with less operational overhead. It combines the core mail protocols and related deliverability tooling in a single project, covering message transport, mailbox access, and browser-based administration. The project is designed for straightforward setup on a dedicated machine or virtual machine, with quickstart instructions that generate configuration files, accounts, DNS guidance, and startup commands. It also includes webmail, an admin UI, account autodiscovery, and operational features such as metrics, logging, reputation tracking, and spam filtering. Mox is intended to be maintainable and extensible, and it exposes a simple HTTP/JSON API for integrations and event delivery.

Cypht is a web-based email client and news reader designed to aggregate mail from multiple accounts into a single interface. It is aimed at users who want to manage several email sources without replacing their existing accounts, while still being able to browse folders and send messages normally. The project is built around a plugin/module-set architecture, allowing functionality to be extended or customized without modifying the core code. The README points users to installation, feature, module, security, and licensing pages, and also provides a Docker image and a Composer package for developers or deployers who want alternative installation paths.

Maddy Mail Server is a self-hosted mail server designed to provide the core pieces needed to run email infrastructure in one daemon. It can send mail over SMTP, accept inbound mail as an MX server, and store messages for access via IMAP. The project also includes several security and deliverability-related protocols such as DKIM, SPF, DMARC, DANE, and MTA-STS. It is aimed at operators who want to replace a stack of separate mail components with a simpler setup and lower maintenance burden. The README notes that IMAP storage is still beta and suggests Dovecot for users who need a more mature IMAP implementation, while still indicating that Maddy can handle message delivery business.

iRedMail is a self-hosted mail server solution intended for administrators who want to deploy and manage a complete email stack on supported Linux and BSD systems. The README presents it as a full-featured platform and points users to installation guides, the project website, and an online support forum. The project emphasizes straightforward deployment options. It can be installed by following the official documentation, and the README also recommends the iRedMail Easy platform for easier deployment, one-click upgrades, and ticket-based support. In addition, an all-in-one Docker edition is available through a separate repository, which suggests the software can be deployed in a containerized form as well.

SnappyMail is a self-hosted, web-based email client built as a faster and more lightweight fork of RainLoop Webmail Community edition. It is aimed at users or administrators who want a modern browser mail interface with reduced JavaScript payloads, improved performance, and a simpler installation footprint. The project emphasizes privacy and security-oriented changes, including removal of several external service integrations, support for stronger encryption options, and updated authentication handling in the admin area. It also adds features such as dark mode, an advanced Sieve script editor, notifications via service workers, and support for Kolab groupware and richer IMAP capabilities. The README points to the project website and wiki for installation instructions and broader product information.