What is an email server?
A mail server is a software package that regulate sending and receiving emails using email protocols over the internet.
Mostly, we are using several email services like Gmail, Outlook and ProtonMail. However, enterprise often require to use their infrastructure services.
Many users and companies tend to have their mail servers to own and maintain their data and keep everything in their control.
In this article we collected the most active and usable open-source mail servers for enterprise and personal use.
Open-source email servers for enterprise and personal use
iRedMail is a free open-source popular mail server package. It has a great portion of open-source email servers running online. It runs on Linux servers like RedHat, Ubuntu, CentOS, Debian, FreeBSD and OpenBSD.
iRedMail uses secure connections with full support for POP3, IMAP, SMTP. Emails are encrypted using TLS.
It features a web client and supports external webmail clients like Reoundcube. It also helps users to manage calendars (CalDav), address books (CardDav).
Server admins can choose their favorite database store backend like MySQL, MariaDB, PostgreSQL and OpenLDAP.
Furthermore, iRedMail has a built-in antispam and antivirus support with third-party extensions like SpamAssassin, ClamAV, SPF and DKIM. All features and configurations are easy to control through a web admin panel, but it comes in two versions a free open-source community version and a Pro version.
hMailServer is our second open-source mail server pick, it is a full-featured email server with similar features like iRedMail, but it works only for Windows Servers.
hMailServer supports the common email protocols (IMAP, SMTP and POP3). It offers a spam protection with 3rd party anti-spamming systems like ASSP and SpamAssassin.
Webmail clients like RoundCube and SquirrelMail are completely supported with hMailServer.
Postal is a complete Libre free mail server for enterprise. It is the open-source equalivent for Sendgrid, Mailgun and Postmark.
Postal supports all known protocols, comes integrated with spam and virus protection. It offers a developer friendly API.
James is an enterprise-specific open-source mail server that built as a cross-platform system with Java and Scala.
James mail server supports all popular email protocols like SMTP, LMTP, POP3, and IMAP, with ManageSieve, JMAP protocols as well.
James offers 3 ways to administrate the system: REST, JMX and Command Line. It offers different options for storage which include: Cassandra DB, MySQL, MariaDB, HSQLDB and ElasticSearch.
Haraka is an open-source SMTP server built with Node.js. It is highly scalable, extensible through plugins.
Haraka runs seamlessly on Windows and Linux servers, and it requires minimal configuration.
Modoboa is a free open-source easy-to-install email server and engine for enterprise. It has what takes to create a fully functional email server similar to commercial services.
It supports multiple domains per single setup, calendar management, address book manager, long list of administration tools that includes monitoring, real-time statistics, security configuration, users and permission manager.
It also comes with a webmail support and multi-lingual support.
DEVECOT is a minimal open-source IMAP and POP3 email server for Linux/ Unix operating systems. It supports different authentication methods, requires minimal memory, supports Postfix and Exim and offers free migrations from other email servers.
DEVECOT features include shared mailboxes with a dozen of other features.
Yet another SMTP mail server for teams and software development. MailSlurper is a lightweight package for personal use or software developers who want to write email-centric applications.
It features a responsive web-based admin panel, email attachments, SSL support, basic user authentications and runs on Windows, Linux and macOS.
An open-source mail server for IMAP and POP3. WildDuck supports large numbers of emails with configurable large quotes because it scales horizontally.
It offers two and multi-factor authentications and released as an open-source under European Union Public License.
WildDuck is built on top of Node.js, Redis and MongoDB
If you are looking for an enterprise freshly developed mail server, then Cuttlefish mail server is a great option. It comes with all required infrastructure to run a seamless email server with a fancy well-designed web email client and web admin dashboard.
Cuttlefish requires Ruby, PostgreSQL, Redis and Postfix.
- Cyrus Mail Server
Cyrus IMAP is a free open-source email, contacts and calendar server that offers speed, security and support for dozens of protocols and authentication methods.
It is a rich configurable mail-server with a large set of options and third-party integrations.
Cyrus is recommended for enterprise and companies which offers emails to their customers.
Mailu is a lightweight but features-rich email server with minimal setup thanks to its Docker image.
Mailu features IMAP, IMAP+, SMTP support, webmail access, multiple admins, quote configuration and forces TLS for external integration. Furthermore, Mailu offers a built-in anti-virus scanner and several antispam methods that include external services.
Mail-in-a-Box is a small minimal mail server package for individuals to help maintain their privacy. It is easy-to-deploy as described by its developers and supports SMTP (postfix), IMAP (Devecot), CardDAV/ CalDAV, and Exchance ActiveSync servers.
Moreover, Mail-in-a-Box has antispam features, backup options, plays well with Linux firewall (UFW), and comes with a dozen of security-focused features.
It works well with webmail like Roundcube, addressbook clients like Nextcloud contact clients and offers a well-designed easy-to-use control panel.
Salmon, also known as Python mail server is a free open-source mail server for developers who wish to create a robust and complex server-based mail applications.
It is released under GNU GPLv3 and works seamlessly with Python web frameworks and libraries like Django and SQLAlchemy.
- Open Trashmail
Open Trashmail is a lightweight trash mail solution for personal users. It comes with a simple web-based email client and Python-powered mail-server backend.
Unlike other heavy-duty mail servers on this list, Open Trashmail does not use any database, rather it uses flat-files for storage.
MailCatcher is a free tiny SMTP mail server for personal usage with a simple web-based mail client. It supports both text and HTML message version, large file attachments, command-line options to override the default SMTP/HTTP and port settings.
As our list came to an end, we have to say that we listed the most updated and usable ones and excluded the old obsolete and abandoned projects. We hope this list will be useful for anyone looking to run his own private email server.
If you think we missed any open-source email server project that need to be on this list please let us know.