Open-source Yahoo Mail alternatives

Mail-in-a-Box helps individuals take back control of their email by providing a one-click, easy-to-deploy mail server in a box. It turns a fresh Ubuntu 22.04 LTS 64-bit machine into a working mail server by installing and configuring the required components. There are no user-configurable setup options, so it is designed to just work.

The installed components include Postfix for SMTP, Dovecot for IMAP, Nextcloud for CardDAV and CalDAV, z-push for Exchange ActiveSync, and Roundcube webmail. It adds spam filtering with SpamAssassin and greylisting with Postgrey, DNS with SPF, DKIM, DMARC, DNSSEC, DANE TLSA, MTA-STS and SSHFP records set automatically, and TLS certificates from Let's Encrypt. Backups use duplicity, with ufw, fail2ban and munin for protection and monitoring.

Project goals include making a good mail server easy to deploy, promoting decentralization and privacy, and keeping configuration automated, auditable and idempotent. It deliberately does not aim to be customizable by power users. Mail-in-a-Box is written in Python, released into the public domain under CC0-1.0, and has a Code of Conduct for contributors.

Stalwart is an open-source mail and collaboration server written in Rust and designed to be secure, fast, robust and scalable. It supports JMAP, IMAP4, POP3, SMTP, CalDAV, CardDAV and WebDAV, so a single server can handle email, calendars, contacts and file storage.

On the email side it offers JMAP for Mail and Sieve, IMAP4rev2 and IMAP4rev1 with ManageSieve, and POP3. The SMTP server includes DMARC, DKIM, SPF and ARC for message authentication, transport security through DANE, MTA-STS and TLS reporting, automated DKIM key rotation, throttling and filtering rules, sieve scripting and milter integration, and distributed virtual queues.

The collaboration features cover CalDAV and JMAP for Calendars, CardDAV and JMAP for Contacts, and WebDAV and JMAP for File Storage, with fine-grained sharing through WebDAV ACL and JMAP Sharing. A built-in spam and phishing filter includes a rule set and LLM-driven message analysis. It is self-hosted software that administrators run on their own servers.

mailcow: dockerized is an open-source mail server package that runs as a set of Docker containers managed with Docker Compose. It bundles the pieces needed to run your own email, so administrators do not have to assemble and configure each component separately.

The stack is built around established open-source software: Postfix for SMTP, Dovecot for IMAP, Rspamd for spam filtering, ClamAV for antivirus scanning, SOGo for groupware and webmail, and ACME support for certificates. A web administration interface sits on top. Topics in the repository also mention the Olefy component for document scanning.

mailcow is released under the GNU General Public License v3 and installed on your own server following the official documentation. It is managed and maintained by The Infrastructure Company GmbH, and the project offers support contracts through Servercow as well as a one-time support payment option. The community gathers on Telegram, Mastodon and GitHub Sponsors.

Mailu is a full-featured mail server delivered as a set of Docker images. The project aims to give people an easily set up and maintained mail server made entirely of free software, without proprietary components or unrelated groupware features and without trackers.

It covers the standard email server functions, IMAP and SMTP with client auto-configuration profiles, along with aliases, domain aliases, custom routing and full-text search of attachments. Users get webmail, auto-reply, auto-forward and managesieve, while admins get global admin roles, per-domain delegation, announcements and quotas. Security features include enforced TLS, DANE, MTA-STS, Let's Encrypt certificates, outgoing DKIM and an antivirus scanner, and antispam features include greylisting, auto-learning, DMARC, SPF and anti-spoofing checks.

Mailu is written in Python and deployed with Docker or Docker Compose. The project's own configuration files, Dockerfiles and code are MIT-licensed, and all bundled components are free software compatible with it. A demo server and website documentation are provided.

Roundcube Webmail is a multilingual IMAP client that runs in the browser and behaves like a desktop application. It offers the functions people expect from an email client, such as MIME support, an address book, folder management, message search and spell checking, without installing anything on their own computers.

It is written in PHP and JavaScript and requires MariaDB, MySQL, PostgreSQL or SQLite as its database. A plugin API makes it extensible, and the user interface can be customized with skins. The client uses jQuery 3.x and inherits its browser support, covering current versions of Chrome, Edge, Firefox and Safari. Releases follow semantic versioning, and the README ships separate install and upgrade guides.

Roundcube is licensed under GPL-3.0 and is installed on a web server that connects to an existing IMAP mail server. Note that the repository README warns that the Git snapshot is not a stable version and should not replace a production installation.

Forward Email is an open-source email service focused on privacy. It handles custom-domain email forwarding and also provides mailboxes accessible over IMAP, POP and SMTP, with encryption using algorithms such as AES-256 and ChaCha20, and it positions itself as an all-in-one alternative to Gmail, Mailchimp and Sendgrid.

Its topics and documentation point to features such as sending mail, newsletters, SQLite-based storage, push notifications, and calendar and contact support through CalDAV and CardDAV, plus autodiscovery records and Domain Connect integration for setting up DNS. The README includes a local development guide and detailed notes on server infrastructure, load balancing, provisioning and deployment, including automated setup with Ansible.

The code is JavaScript and the project says it is fully open source, so the service can be inspected and, with the published infrastructure guidance, run on your own servers. Most consumers simply use the hosted service at forwardemail.net. It suits individuals and small organizations that want private email on their own domain and developers interested in how such a stack is built.