14 Best Linux Mail Server in 2022 (Free + Open Source)

14 Best Linux Mail Server in 2022 (Free + Open Source)
Updated on June 22, 2022
13 mins read

Ever had a marketing email from this or that company? Who hasn’t, right? So, even if you have been using Gmail or another free mail service until now, you’ve had quite a few run-ins with mail servers. The universal use of emails in everything from internal communications to marketing have made mail servers a huge issue. So, if you’re looking to discover the best mail servers for Linux (or just to find out if you need one), you’ve come to the right place.

With the clear importance of mail servers, it is difficult to imagine launching a successful business without taking advantage of the best mail servers. To manage your daily backlog of emails, you need the best Linux email server around. This article will help you select the best Linux mail server from a list of 10 contenders. Let us now dive in to learn more about the top 14 of the best mail servers for Linux OS.

What is a Mail Server (and Why Should You Care?)

As a user, we all have some experience with email clients like Microsoft Outlook or Thunderbird. But when you go from being a user to trying to start your own business, you will come to see the other side of emails: mail servers.

A mail server is basically a software application used to transfer emails from one point of the Internet to another. Also known as Mail Transfer Agents (MTAs), they receive incoming emails from other servers before forwarding them to the user’s client software. They also do the opposite, receiving emails from the user and forwarding them to another server.

There are actually two sides to mail servers as well. Although almost all mail servers handle both incoming and outgoing emails, the two functions are separate, and follow different protocols. An incoming mail server usually operates using the Post Office Protocol 3 (POP3) or the Internet Message Access Protocol (IMAP). While the more popular POP3 is more storage-efficient (it deletes emails it has sent to the client software), IMAP is more secure and customizable.

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On the outgoing side, most mail servers use the Simple Mail Transfer Protocol (SMTP) to send the emails they have previously received from the user’s client software. There are some mail servers that also support the more secure Extensible Messaging and Presence Protocol (XMPP). So, make sure to look out for which of the candidates support these different protocols — that will tell you a lot about what you can expect from them.

Using top mail servers is one of the key methods to increase the business revenue in the long run. The best mail servers are easy and smart resources that can help you achieve better communication and marketing results. They open a new way to expand customer acquisition and retention for your business, no matter its size.

How to choose the best windows mail server?

When looking for a mail server, there are many things you need to consider.

The most important factors are the features the server offers and how well it meets your needs. Some of the features to look for include support for different mail clients and integration with your existing software and hardware. Make sure the mail server has the features you need to run your business efficiently.

Another important factor is the size of your organization. If you have a small business with only a few users, then a small mail server may be all you need. However, if you have a large number of users, then you'll need a more powerful server.

You should also consider the cost of the server and whether or not it will fit into your budget. They can range in price from several hundred dollars to thousands of dollars.

Before you make a final decision, be sure to test out several different servers to find the one that is right for you. This will help ensure that you are getting the best possible service and that you are happy with your choice.

What are the best mail Servers for Linux?


One of the best Linux mail servers for Linux that can also be used in Windows NT is Sendmail. As it is mentioned in Mailserver.com, it is the No.1 MTA (Mail Transfer Agent) in use today. Sendmail is a general-purpose email routing facility with its first version released in 1983.

An MTA well known for being free (there is also a proprietary version), open-source, and based on UNIX, Sendmail 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:

  • Reliability in message delivery

  • Needs very little network bandwidth

  • Customized email forwarding capabilities

  • Using configuration files to control mail configuration

exim mail server

This is a mail transfer agent developed at the University of Cambridge. Distributed under the GNU (General Public License), Exim aims to be one of the most flexible mailers with a great number of features for checking incoming emails. Exim is free software that has been incorporated into most UNIX-like systems. Its fourth version is the default MTA on Debian Linux systems. Some of the best features of this mail server are:

  • The external authenticator

  • Pre-built support for a large number of database management systems such as MYSQL, Oracle DB, SQLite, PostgreSQL, and Redis

  • Encrypted SMTP connections using SSL/TLS

  • Straightforward configuration, customization, and task management

  • Three log mechanisms i.e. main log, panic log, and reject log

  • Local scan function

  • System-wide message filtering

  • Message processing

  • GNU GPL license

postfix mail server

It was first released in 1998 under the IBM Public License 1.0, 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 emails. 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:

  • Junk mail control

  • Database support

  • Fast and secure

  • Flexibility in administration

  • Convenient log management

  • Defense against spambots

  • Pre-packed content filtering

  • Virtual domain support

  • Configurable status notification

  • 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.

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axigen mail server

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 connectors) 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:

  • Integrated mailing list server

  • Fully Automatic Migration Tool (without the need of the legacy accounts passwords)

  • Antivirus and Antispam integration options

  • Malware and Spam Protection Mechanism

  • Providing a convenient address book

  • Unmatched manageability for administrators

  • Various mobile capabilities including mobile-friendly webmail and Exchange Active Sync support

  • Can be hosted in data centers, on bare-metal, private or public cloud servers

  • Multiple, customizable advertising and branding options

  • Integrated Web-Admin and Web-Mail client

  • 60-day, Full-Featured Trial

  • Highly configurable platform

citadel mail server

Without any doubt, this is one of the best mail servers for Linux and UNIX. Despite the initial release 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 storage.

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

  • Shared calendar

  • Instant messaging

  • A convenient address book

  • Scheduler

  • File storage

  • Jabber alongside SSL/TLS encryption

  • OpenSSL encryption

  • Built-in implementations of Internet Protocols such as POP3, IMAP, SMTP, and XMPP

  • Web-based user interface based on Ajax style functionality for application-like interactions

  • OpenDAP and Microsoft Active Directory support


Modoboa is one of the best open-source SQL-based Linux mail servers, which accesses a set of useful features from one user interface that does not require installing each capability individually. It offers a secure and private mailing method using the TLS protocol Let’s Encrypt which is a nonprofit Certificate Authority. It also makes you free of email providers’ dependency.

Modoboa is widely deployed with SPF and DKIM protocols using DMARC. These protocols are free email authentication technologies for email delivery and email security that, through a reporting function, help senders and receivers boost and monitor the protection of the domain against fraudulent email. The nice thing is that it lets you configure a fully-functional mail server through the most important features you can benefit from which include:

  • Webmail

  • Calendars management

  • Address books management

  • Creating visualized filtering rules to organize emails

  • auto-responder

  • Supporting numerous creation of domains, mailboxes, and aliases

  • Administrator tools that help you monitor the traffic

  1. Qmail

Qmail is among the best Linux mail servers. It is one of the most widely-used mail servers. It is an excellent replacement for Sendmail. It offers different kinds of benefits for users and security is the biggest one; the SMTP protocol verifies this claim by providing different credentials through the queue manager or the SMTP sender. Also, the simple and easy configuration makes it popular as one of the best Linux mail servers. Some of its notable features are listed below:

  • QMT support

  • Supporting different platforms such as Linux, Solaris, Mac OSX, and BSD

  • Offering EZMLM mailing list manager, VERPs, and automatic host configuration

  • Having a modular-based system (It allows you to replace any single part of the system with an alternative module)

  • Managing custom mailing lists and supporting the automatic prevention of mailing loops

  • User-controlled wildcard mailboxes

hmail server

hMailServer is another free, open-source Linux mail server that is popular among a variety of industries. It comes with built-in anti-spam technology, including SPF and SURBL. It supports main protocols such as IMAPP, SMTP, and POP3. Moreover, it has simple installation and configuration and is associated with a high-security feature that enables authentication. Hmailserver important features include:

  • SSL encryption

  • website administration

  • Using built-in backup

  • Scanning all incoming and outgoing emails

  • Multi-domain supports

  • Offering custom SMTP routes for particular domains

Best control panels for Linux (Updated List for 2022)


Best control panels for Linux (Updated List for 2022)
cyrus imap

The Cyrus IMAP server is a powerful Linux mail server that helps you access your private mails via IMAP protocol. It also covers contacts and calendar services. Having multiple services attached to a mail server improves your business performance. Users can access the mail server through IMAP, IMAPS, POP3, POP3S. You can benefit from a private mailbox database that optimizes the server efficiently, with scalability and administration. The list below are a few features of Cyrus IMAP server:

  • JMAP support

  • Supporting antivirus and anti-spam toolkits

  • Handling deliverability through SPF, DKIM, DMARC

  • Using mail filtering

  • Fully authentication options through Cyrus SASL

  • Deploying consistent software updates

  • Supporting access control lists on mailboxes

mail in a box

Mail-in-a-Box is an easy-to-use Linux mail server provider which uses the latest security solutions. It provides you with useful services such as automatic DNS configuration, spam filtering, greylisting, backups to Amazon S3, static website hosting, and easy SSL certificate installation. This tool aids in providing a hosted mail for multiple users and DNS and delivers the webmail and an IMAP/SMTP server for mobile and desktop mail software. The features of Mail-in-a-Box include:

  • Using web-based control panel for email configurations and settings

  • contacts and calendar synchronization

  • Free TLS (SSL) certificates from Let’s encrypt

  • Implementing modern mail protocols (SPF, DKIM, and DMARC) and the latest security practices, including opportunistic TLS, strong ciphers, and HST


SquirrelMail, licensed under the GNU General Public License, is one of the most popular Linux mail servers. This free server is written in PHP and supports the IMAP and SMTP protocols.

It's easy to set up and use, and its pages are rendered in HTML 4.0. It can handle large volumes of mail, and it's very reliable. SquirrelMail also supports spam filtering and security features like SSL encryption. It can also be used with most major web-hosting providers and integrates well with other applications such as WordPress. Other features of SquirrelMail include:

  • Supporting pure text mails

  • Supporting reading and sending HTML email messages

  • Having a spell checker

  • Providing an address book to store email addresses

  • Having the ability to search and flag emails

  • Having a proxy server for IMAP protocol

  • Using mail filtering


Zimbra Email Server is an open source powerful Linux mail server that comes with a variety of features. It's easy to use, scalable, and secure. In addition, it supports a number of different devices and operating systems. This makes it a great choice for businesses of all sizes. Zimbra also has a great community of users who are always willing to help out.

If you're looking for an email server that can meet your needs, Zimbra is a great option. It's been used by millions of people around the world and is known for its reliability and security.

It provides users with so many features, such as:

  • Having group calendars and document sharing

  • Having a mobile web client application

  • Supporting both private and public cloud

  • Customizable

  • Provides a backup feature

  • Having an Email management

  • Providing an Instant messaging feature


The Horde Project is a webmail and collaboration suite that provides an email server, tasks and notes functionality, contact management, and more. The software is written in PHP and is licensed under the GNU General Public License.

This Linux mail server is easy to use and navigate and can easily be scaled up or down to meet your needs. It is designed to work with any size organization, and its team is always on hand to help with any questions or problems you may have. Here are some of its other features:

  • Shared calendars, contacts, reminders, IMAP files, and tasks

  • Supports IMAP, POP3, 3-pane, and 3-column layouts, HTML messages

  • Provides message filtering

  • Supports News feed

  • Supports mobile email access

  • Have advanced productivity tools

  • Have spell checker

  • Filter mails

  • Search emails

  • Threaded conversation view


Apache James is a popular open-source Linux mail server. It’s easy to set up and configure and is a great option for those who need an email server that can handle a high volume of messages. It's also perfect for businesses that need to comply with strict email regulations.

Apache James can be used as a standalone server or as part of a larger infrastructure. It supports both SMTP and IMAP protocols, and it can be used with a variety of different mail clients. Apache James also has a wide range of features, including:

  • Supports SMTP, LMTP, JMAP, POP3, IMAP, and ManageSieve

  • Email management

  • Store the message data

  • Filtering spam emails

Best Linux Mail Server Antivirus 2022 + Tips for Securing Your Linux Email Client🛡️


Best Linux Mail Server Antivirus 2022 + Tips for Securing Your Linux Email Client🛡️

Free SMTP server Linux

SMTP servers can be used for a variety of purposes, the most common of which is to send and receive emails.

Small businesses and individual users are always looking for free SMTP servers. There are many different SMTP servers for both Windows and Linux available on the internet. Some of them are free, while others charge a fee. The best SMTP server is one that is reliable, fast, and easy to use.

The best SMTP server Linux is undoubtedly Sendmail. Sendmail is very powerful and has many features that other SMTP server applications lack. It's open-source, feature-rich, and easy to configure. Plus, it's free!

Open source mail server Linux

Open source mail servers are becoming more and more popular as businesses and individuals search for ways to cut costs and increase efficiency. But what is an open-source mail server? And why are they becoming so popular?

An open-source mail server is a type of server that uses software that is freely available to the public. This means that the code used to create the software can be modified and improved by anyone who chooses to do so.

An open-source mail server Linux is a great alternative to expensive commercial options. It can be configured to your specific needs, and it's free! There are many different open-source mail servers available for Linux, so do your research to find the best one for you.

Be sure to evaluate the features that are important to you, such as spam filtering, virus protection, and user support. Once you have chosen a server, be prepared to spend some time configuring it to meet your needs.

There are several reasons why open-source Linux mail servers are becoming so popular:

First, they are often cheaper than their proprietary counterparts.

Open-source software is typically free to download and use, while proprietary software can be expensive.

Additionally, open-source software tends to be more reliable and secure than proprietary software, as it has been tested by many people over a longer period of time.

Which Email Protocol Is Capable of Sending Emails? (SMTP, IMAP, and POP)


Which Email Protocol Is Capable of Sending Emails? (SMTP, IMAP, and POP)

Final Word: Choosing the Best Linux Mail Server

In this blog post, we reviewed the top ten best Linux mail servers. Choosing any one of these mail servers depends on the specific needs of your business, but honestly, we do have favorites. As far as our preferences go, Citadel and Modoboa are the clear winners of this 10-sided competition.

Aside from choosing the best Linux mail server based on your own preferences, however, you should also choose a good Linux hosting provider. Even the best mail server cannot perform well when your server is down or acting up. A decent but affordable VPS is perhaps the best way to start out or even expand to a mid-sized online business.

Here at Cloudzy, our Linux VPS  services provide you with robust infrastructure and ultrafast connections, giving you a secure and safe hosting experience at affordable prices. Plus, our next-gen SSD storage with NVMe protocol and DDR4 RAMS helps you improve your users’ experience. We provide services to businesses of any size. We offer Linux VPS in more than 15 global locations with extensive peering and minimal latency.


What is Mail Server in Linux?

A Linux Mail Server is software running on Linux used for transferring emails between another server and client software. There is numerous Linux mail server software with different features and advantages.

Which Linux Mail Server is the Best in 2022?

The answer, of course, changes based on what you are planning to do with it. Citadel and Modoboa are comprehensive enough to cover most demands, but you should take a look at the list for yourself.

Is Microsoft Outlook a mail server?

No, it’s not, actually. It’s a mail client software used to communicate with a mail server. It is a common misunderstanding, however, since it is what most users think about when they hear the words “mail server.”


Mary is a creative author who believes content is all about fulfilling users' needs and concerns. She always tries to provide the best solutions for her audience.


Your Review

    hgdnimfFeb 1, 2021, 9:19 AM

    What is the difference between mail server for windows and Linux? Because I saw that you have an article for windows mail servers too and I want to know do they work differently or what?

    CloudzyOct 23, 2021, 7:52 AM

    The difference between Windows and Linux mail servers goes back to the difference in the core of these two operating systems. In terms of performance from the user's side, there's no considerable difference. Thank you so much for taking your precious time to read our blog 🌻💛

    kngehgdbtJan 19, 2021, 5:24 PM

    Thanks for this great article I introduced one of these mail servers to one of my friends and he is quite satisfied

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