Mail Servers for Linux (Top 5)

Mail server, MX host, mail exchanger, message transfer agent, mail transfer agent (MTA), or mail relay are the terms used for software that transfer electronic mail messages from one system to another. In this article, we will introduce the best mail servers for the Linux OS.

Sendmail:

One of the best mail servers for Linux that can also be used in Windows NT is Sendmail. As in Mailserver.com is mentioned, this is the №1 MTA in use today. A general-purpose internet network email routing facility that its first version was released in 1983. It is an MTA that is well known for being free (it also has spread as a proprietary software), open-source, and based on UNIX. One of the oldest and most used mail transfer agents that provides a versatile set of delivery methods for sending emails.

When a Sendmail server receives an e-mail, it attempts to immediately deliver that to the intended recipient. If the recipient is not present, it queues messages to deliver them later. In fact, it doesn’t provide any mailbox facility. So, other software such as Internet Message Access Protocol and POP3 are needed. Some of the best features of this Linux mail server software are:

1. Reliable in message delivery.
2. Need very little network bandwidth.
3. Customized email forwarding facilities.
4. Using configuration files to control mail configuration.

Exim

This a UNIX-like mail transfer agent developed at the University of Cambridge. Distributing under the GNU General Public License, it aims to be one of the most flexible mailers with a great number of facilities for checking incoming e-mails. Exim is a free software that has been ported to most UNIX-like systems in which the fourth version is the default MTA on Debian GNU/Linux systems. Some of the best features of this mail server are:

1. The external authenticator.
2. Pre-built support for a large number of database management systems such as MYSQL, Oracle DB, SQLite, PostgreSQL, and Redis.
3. Encrypted SMTP connections using SSL/TLS.
4. Straightforward configuration, customization, and task management.
5. Three log mechanisms named main log, panic log, and reject log.
6. Local scan function.
7. System-wide message filtering.
8. Message processing.
9. GNU GPL license

Postfix

It was released under the IBM Public License 1.0 that is a free software license. It was first released in 1998, and now, is available under the Eclipse Public License. Postfix is also known as IBM Secure Mailer and VMailer. It runs on BSD, AIX, HP-UX, Linux, macOS, Solaris, and every UNIX-like operating system with a C compiler and POSIX development environment. This powerful, and open-source mail server can be used for routing and delivering e-mails. It is the default message transfer agent for Ubuntu, RedHat /CentOS, NetBSD, and macOS. Some of the most important features of this Linux mail server are listed below:

1. Junk mail control.
2. Database support.
3. Fast and secure.
4. Flexibility in administration.
5. Convenient log management.
6. Defense against spambots.
7. Pre-packed content filtering.
8. Virtual domain support.
9. Configurable status notification.
10. Support for many standard databases including MYSQL, SQLite, PostgreSQL, LDAP, Memcached, CDB, and Berkeley Database.

This mail server consists of a large number of programs that run in the background and a few programs that interact with the user processes. You can imagine the whole system as a router because it looks at the IP packet, and determines the destination and resource IP address exactly like a router. Then, it selects the right interface to route the mail toward its destination.

Axigen

Axigen is one of the best mail servers for Linux, Microsoft Windows, and Docker that supports POP3, SMTP, IMAP, and webmail. It comes with groupware and collaboration functionalities (like calendars, notes, tasks, and outlook connector) that can be completely free. The development of this mail server began in 2003 based on innovative proprietary technology. It supports all demanding users from small businesses to large service providers. Some of the good features of this mail server are:

1. Integrated mailing list server.
2. Fully Automatic Migration Tool (without the need of the legacy accounts passwords).
3. Antivirus and Antispam integration options.
4. Malware and Spam Protection Mechanism.
5. Providing a convenient address book.
6. Unmatched manageability for administrators.
7. Various mobile capabilities including mobile-friendly webmail and Exchange Active Sync support.
8. Can be hosted in data centers, on bare-metal, private or public cloud servers.
9. Multiple, customizable advertising and branding option.
10. Integrated Web-Admin and Web-Mail client.
11. 60-day, Full Featured Trial.
12. Highly configurable platform.

Citadel

With no doubt, this is one of the best mail servers for Linux and UNIX. In spite of the initial release backed to 33 years ago, it passes the test of time because of its superior performance and flexible features. This mail server is a general-purpose groupware and collaboration suite that is designed to run on open-source operating systems such as Linux, and BSD UNIX distributions (but supports most systems). It uses the Berkeley Database for all of its data stores.

It is an open-source and free software that works under the license of GNU General Public License (GPLv2 and GPLv3). This Linux server is mostly known for its simple control panel and efficient runtime. Moreover, it has a lot of good features that some of them are listed below:

1. Shared calendar.
2. Instant messaging.
3. A convenient address book.
4. Scheduler
5. File storage.
6. Jabber alongside SSL/TLS encryption
7. OpenSSL encryption.
8. Built-in implementations of Internet Protocols such as POP3, IMAP, SMTP, and XMPP.
9. Web-based user interface base on Ajax style functionality for application-like interactions.
10. OpenDAP and Microsoft Active Directory support.

In conclusion:

A great number of features, technologies, and software can be found in the world of mail servers. Most of them are made of Mail Delivery Agent (MDA) and Mail Transfer Agent (MTA). They can support various protocols such as POP3, IMAP, SMTP, XMPP, SSL, and IPv6. Some of them are working on various operating systems like Windows, and Linux. In this article, we introduced you five of the best mail servers for Linux. Have you any experience related to running any of them? Please share it with us.