Email

14 Best Free and Open Source Email Servers

Email remains the killer information and communications technology. Email volume shows no sign of diminishing, despite the increasing popularity of collaborative messaging tools. There were over 350 billion emails sent in 2023.

Messages are exchanged between hosts using the Simple Mail Transfer Protocol with software programs called mail transfer agents, and delivered to a mail store by programs called mail delivery agents, frequently referred to as email clients.

Within the Internet email system, a message transfer agent, or mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using SMTP. The terms mail server, mail exchanger, and MX host are also used in some contexts.

Here’s our verdict on the finest email servers for Linux. All of the servers are published under an open source license.

Ratings chart

Let’s explore the 14 email servers. For each title we have compiled its own portal page, a full description with an in-depth analysis of its features, together with links to relevant resources.

Email Servers
EximHighly configurable mail transfer agent
OpenSMTPDImplementation of the server-side SMTP protocol with additional extensions
moxModern, secure, all-in-one email server
DBMailEnables storing and retrieving mail messages from a database
WildDuckOpinionated email server
PostfixPopular mail transfer agent
DovecotSecure POP3 server that supports mbox and maildir mailboxes
CourierIntegrated mail/groupware server
Cyrus IMAPEmail, contacts and calendar server
ZimbraZimbra Collaboration Suite
CitadelExchange-killer groupware server
chasquidSMTP server with a focus on simplicity, security, and ease of operation
SendmailMail transfer agent for sophisticated mail configurations
qmailWritten as a more secure replacement for the Sendmail program

This article has been revamped in line with our recent announcement.

Best Free and Open Source SoftwareRead our complete collection of recommended free and open source software. Our curated compilation covers all categories of software.

The software collection forms part of our series of informative articles for Linux enthusiasts. There are hundreds of in-depth reviews, open source alternatives to proprietary software from large corporations like Google, Microsoft, Apple, Adobe, IBM, Cisco, Oracle, and Autodesk.

There are also fun things to try, hardware, free programming books and tutorials, and much more.
Subscribe
Notify of
guest

This site uses Akismet to reduce spam. Please read our FAQ before making a comment.

10 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments
ragvaiv@gmail.com
ragvaiv@gmail.com
3 years ago

In this list, I miss “Kolab”, which is a true fully Open Source Groupware (no restrictions) and has almost all professional features out of the box.

Harri
Harri
2 years ago

Opensmtpd is missing in this list. It is the standard smtp implementation on OpenBSD, but it is available on major Linux distros as well. Very lightweight to configure.

Claudio Ivan de Miranda
Claudio Ivan de Miranda
11 months ago

Ok

Raggovaivo
Raggovaivo
10 months ago

After migration to Debian 12, I replaced my Kolab Groupware with iRedMail (I also tested Modoboa).
iRedMail and Modoboa are both worth mentioning.

Ricardo
Ricardo
1 month ago

How are this servers graded?
What makes exim so much better than postfix, for example?
The individual pages provide no info or criteria for the scoring system

Erik Karlsson
Editor
1 month ago
Reply to  Ricardo

In the past, we published multiple ratings charts rather than an overall rating but people complained the articles were too long. So we publish just the overall ratings chart. The other charts are still prepared but only supplied to people who help the site.