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 330 billion emails sent in 2021.
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 email servers for Linux. All of the servers are published under an open source licence.
Let’s explore the 12 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.
|Exim||Highly configurable mail transfer agent|
|DBMail||Enables storing and retrieving mail messages from a database|
|OpenSMTPD||Implementation of the server-side SMTP protocol with additional extensions|
|Zimbra||Zimbra Collaboration Suite|
|Postfix||Popular mail transfer agent|
|Courier||Integrated mail/groupware server|
|Cyrus IMAP||Email, contacts and calendar server|
|Dovecot||Secure POP3 server that supports mbox and maildir mailboxes|
|Citadel||Exchange-killer groupware server|
|chasquid||SMTP server with a focus on simplicity, security, and ease of operation|
|Sendmail||Mail transfer agent for sophisticated mail configurations|
|qmail||Written as a more secure replacement for the Sendmail program|
Read our complete collection of recommended free and open source software. The collection covers all categories of software.
The software collection forms part of our series of informative articles for Linux enthusiasts. There's tons 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.