E-mail has proved to be the fastest and reliable communication medium of our time. From businesses to individuals, we all rely on e-mails due to the convenience they offer. If you ever wondered how computers send these seemingly simple messages over the network, then follow us through this guide. There are mainly two software components at the heart of e-mail communication, namely the mail server and mail client. The mail server is responsible for transmitting e-mails from node to node on a network, typically the Internet. And the client allows users to retrieve these emails. In this guide, we’ll solely focus on the Linux mail server. Check out another guide to learn more about various Linux mail clients.
Top-Notch Linux Mail Server
Like many other software departments, Linux offers some of the best Mail Transfer Agents(MTA)s. Our editors have gone through a massive selection of these tools and selected the 20 best Linux mail servers for you. These include both open source mail servers and proprietary ones. Stay with us to find out more about various Linux email servers in detail.
1. Exim
Exim is a feature-rich mail server used on many Unix-like operating systems such as Linux and BSD. It also provides efficient cross-platform support, making it a perfect choice for mail servers that need to be diverse and handle a large number of requests.
Being written entirely in C, Exim offers excellent performance and works great even in legacy systems. Moreover, the development team rolls out frequent updates and takes care of bug fixes very well.
Features of Exim
- Exim is arguably among the best mail transfer agents when it comes to customization and configuration abilities.
- It features three different log mechanisms for preventing email spamming, namely the main log, panic log, and reject log.
- Exim comes with pre-built support for a wide range of database management systems such as MySQL, PostgreSQL, SQLite, Oracle DB, and Redis.
- The GNU GPL license featured by this Linux mail server allows admins to modify the software based on their requirements freely.
2. Postfix
Postfix is an immensely powerful open source mail server that can be used for routing and delivering e-mails. It offers a robust set of useful features, including junk mail control, database support, convenient log managements alongside many others.
According to a recent study, more than 30% of the publicly reachable mail servers in the world run Postfix. So there is plenty of useful documentation available that can help users adapt much faster.
Features of Postfix
- Postfix implements top-notch defense mechanisms against spambots and malware while also allowing admins to leverage additional software for filtering.
- It comes pre-packed with a powerful content filter, access control mechanism, virtual domain support, configurable status notifications, and many more.
- It offers quite superior performance, clocking over 300 e-mail deliveries per second from a single Postfix instance.
- This Linux mail server supports many standard databases, including MySQL, Memcache, SQLite, PostgreSQL, LDAP, CDB, and Berkely Database.
3. Zimbra Email Server
Zimbra Collaboration Suite (ZCS) is an open source software framework that provides a powerful yet efficient mail server for Linux users. It offers a robust set of additional features, including group calendars and document sharing with flexible tooltips, drag-and-drop items, and convenient UI menus.
Zimbra ships ready for private and public clouds and offers an innovative mobile web client application. They also provide an immensely powerful closed-source enterprise edition.
Features of Zimbra Email Server
- Zimbra offers real-time backup and restores capabilities, allowing enterprises to focus more on their services rather than security.
- The robust one-click disaster recovery feature makes it very easy to restore sensitive information in case of any server failure.
- Zimbra comes with powerful migration tools that make transferring messages effortless and efficient.
- It allows admins to schedule emails conveniently by using filters like future date, time, and even time zone.
- The robust web administration console provided by this Linux email server makes managing your requests hassle-free.
4. Axigen
Axigen is a powerful email server software with a robust set of innovative features to make email management hassle-free. It provides a massive collection of pre-built features such as an integrated mailing list server, malware and spam protection mechanisms, and various mobile capabilities. Most Linux distributions support Axigen, but the server is not free of charge. However, Axigen also offers a free version with support for up to 5 domains, 5 groups, and 5 users.
Features of Axigen
- This Linux email server is an on-premise software, meaning it can be hosted in data centers, bare-metal, or Private/Public Clouds.
- Axigen provides a convenient address book, a tool for importing/exporting contacts, robust filtering mechanisms, and an innovative mobile WebMail interface.
- It offers modern-day security tools such as encryption, multi-layer access control, blacklisting/whitelisting contacts, and password expiration rules.
- Axigen can access user emails from external sources such as Gmail, Yahoo! Mail and access messages directly from smartphones.
5. Citadel
Citadel is, without any doubt, one of the best open source mail server software available right now. It is an age-old server software and stood the test of time due to its flexible features and superior performance. Citadel is a groupware software, and collaborations take place very frequently.
It was designed to run on Linux and BSD Unix distributions but supports most systems. This Linux server tool is known for its simple yet useful control panel alongside its efficient runtime.
Features of Citadel
- Citadel comes with its own implementation of standard server protocols such as SMTP, IMAP, Sieve, POP3, GroupDAV, and XMPP.
- It provides a convenient address book, scheduler, file storage, and Jabber alongside SSL/TLS encryption for all protocols.
- Citadel supports OpenLDAP and Microsoft Active Directory and can be used for high-speed server-to-server replication.
- It utilizes the Berkely DB database for storing all of its contents, including the messages and knowledge base.
Download Citadel
6. Sendmail
Now known as Proofpoint, Sendmail is one of the oldest and most used mail transfer agents on Unix platforms. It is a general-purpose internetwork mail routing facility that provides a versatile set of delivery methods for sending mails over the Internet.
This mail server software is written by Eric Allman and features customized licensing. Sendmail used to dominate the email server scene before the emergence of modern mail server software such as Exim and Postfix.
Features of Sendmail
- Sendmail is exceptionally reliable and makes sure each message is delivered to the correct destination without much trouble.
- It requires very low network bandwidth because it can batch addresses to a single host.
- Sendmail allows users to specify customized email forwarding facilities without modifying the domain-wide aliases.
- Instead of compiling the configuration instructions before runtime, Sendmail utilizes configuration files to control mail configuration.
7. Qmail
Qmail is a widely used mail transfer agent that was initially developed to be an alternative for the Sendmail program. It is written using the C programming language and thus offers more than efficient performance. Qmail employs various security measurements to reduce mail spamming as much as possible and provides an easy way to set up user-defined mailing lists. Qmail is a public domain software and an excellent option for people searching for open source mail server software.
Features of Qmail
- Qmail is available on a plethora of platforms, including Linux, Solaris, Mac OSX, and BSD.
- It comes with in-built support for the ezmlm mailing list manager, VERPs, and automatic host configuration.
- This Linux mail server software design is extremely modular and allows users to replace part of the software quickly with other modules.
- Qmail allows users to manage their custom mailing lists and supports the automatic prevention of mailing loops.
8. Modoboa
Modoboa is a modern-day mail transfer agent which provides users with a powerful mail hosting and management platform. It comes with a simple yet effective web-based user interface which makes managing the mail server completely hassle-free. The software is known for its versatility and allows easy integration with well-known MTA software such as Dovecot and Postfix. It uses a SQL database as its central point of communication and is written using Python.
Features of Modoboa
- The robust admin panel of this Linux mail server software makes managing domains, mailboxes, and aliases easier than ever.
- Modoboa features an innovative built-in monitor that allows users to visualize their server traffic via handy filtering facilities.
- It utilizes standard server protocols such as DKIM and DMARC for making sure each mail is delivered correctly.
- Modoboa comes with a handy calendar that allows admins to manage hectic timetables much more conveniently.
9. iRedMail
If you’re looking for a full-fledged open source mail server for Linux and BSD distributions, iRedMail is an excellent choice for you. It is a powerful tool with features focused on security, privacy, and secure management. The software consists of all open-source components, and an active development community makes sure bug fixes and frequent updates take place now and then. Their professional tech support also makes sure your communication isn’t interrupted in case of system failure.
Features of iRedMail
- iRedMail establishes all of its mail services using secure connections (POP3/IMAP/SMTP over TLS, webmail with HTTPS).
- It implements powerful encryption mechanisms such as SSHA512 and BCRYPT (BSD) for storing passwords.
- The robust Web UI of iRedMail makes managing emails, folders, and sieve filters very intuitive and efficient.
- It provides a versatile set of storage choices for the backend, including OpenLDAP, MySQL, MariaDB, PostgreSQL.
10. Mail-in-a-Box
Mail-in-a-Box is an innovative modern-day Linux mail server with a primary focus on easy deployment. Each instance of this email server provides handy webmail and an IMAP/SMTP server with automatic DNS configuration. It also allows admins to back up their mail server to Amazon S3. The free TLS(SSL) certification of this software is provided via Let’s Encrypt. The software employs the best security practices to make sure all communications are handled securely and decreases the attack surface significantly.
Features of Mail-in-a-Box
- It comes pre-installed with modern-day mail protocols such as SPF, DKIM, and DMARC alongside extremely secure ciphers.
- Mail-in-a-Box allows users to host emails for multiple domains and users.
- The software is licensed under the GNU GPL 3 and thus requires no charge at all.
- It comes with in-built support for spam filtering, greylisting, and static website hosting alongside many more.
11. Kolab Groupware
Kolab Groupware is an open source collaboration suite that features many web utilities such as an email server and multiple web frontends. The open source mail server provided by this suite is superior to many enterprise-grade products and can be used for delivering large-scale emails consistently.
No matter how much traffic you intend to handle, Kolab allows you to it very efficiently. It also has an enterprise edition that offers top-notch tech support alongside additional premium functionalities.
Features of Kolab Groupware
- Kolab Groupware has in-built support for all standard web protocols such as SMTP, POP3, IMAP, and DANE alongside ActiveSync and Sieve.
- It offers exceptional central storage support and can easily be integrated with directory service, mail delivery systems, and other assets.
- Kolab allows admins to filter emails based on pre-defined criteria and reduces spam as much as possible.
- Users can save and share files from anywhere using Kolab’s integrated cloud service.
12. Apache James
Apache James, also known as Java Apache Mail Enterprise Server, is a powerful Linux email server software developed and maintained by the Apache Software Foundation. This program is written entirely in the Java programming language and provides some of the most sought-after email server functionalities. The modular architecture of Apache James makes it efficient than many traditional mail servers and allows users to assemble their mail server using ready-made components.
Features of Apache James
- This email server comes with native support for SMTP, LMTP, POP3, IMAP, ManageSieve, and JMAP.
- Apache James allows users to choose from a wide range of storage options, including MySQL, PostgreSQL, HSQLDB, Cassandra, and ElasticSearch.
- It can be administered using either JMX or the command-line alongside robust REST APIs.
- The software is entirely independent and can be extended for additional functionalities easily using tailor-made plugins.
13. Courier Mail Server
The Courier Mail Server is a proven mail transfer agent that offers individual services for ESMTP, IMAP, POP3, SMAP, webmail, and mailing list. It is widely known as an IMAP server and runs on all POSIX-compliant platforms, including Linux, Mac OS X, FreeBSD, and Solaris. The software is marketed under GPL terms, and hence, is free to use and modify. It is written using a combination of C, C++, and Perl programming languages.
Features of Courier Mail Server
- This mail server software supports many standard databases, including Berkeley DB, MySQL, and PostgreSQL.
- The web-based administration and configuration tool of Courier Mail Servers makes managing emails much more comfortable.
- It offers a built-in IMAP/POP3 aggregator proxy that can distribute all mailboxes between multiple servers.
- Courier Mail Server comes with an integrated email filtering mechanism which helps in reducing spam significantly.
14. Zentyal Server
Zentyal is an open source email and groupware solution based on Ubuntu and is available for all major Unix distributions. It is not just your everyday Linux mail server but can be viewed as a full-fledged network management package. It offers both proprietary and community editions and is designed to meet the ongoing communication demand of small to medium-sized businesses. Some of its additional feature set includes directory and domain server, proxy gateway, and mobile sync.
Features of Zentyal Server
- It offers powerful antivirus and mail filtering mechanism to reduce spam and thwart email attacks.
- Zentyal comes with in-built support for unlimited virtual mail domains and single sign-on authentication.
- The mail server supports ActiveSync and webmail alongside SMTP, POP3, IMAP, CalDAV, and CardDAV protocols.
- Zentyal’s professional tech support makes it a suitable choice for enterprises.
15. Dwarf Mail Server
The Dwarf Mail Server is a simple yet useful Linux SMTP server with a rich set of email management features. It employs the SMTP, POP3, and IMAP4 rev1 protocols for delivering and routing emails via the Internet and can handle unlimited virtual domains.
This server software is based on the Dwarf framework and thus shares many common design principles and features. Overall, Dwarf Mail Server is a lightweight alternative to full-fledged mail transfer agents.
Features of Dwarf Mail Server
- Dwarf Mail Server comes with in-built agents that provide flexible logic layer and offers robust mail filters.
- The software is built on top of Java and thus supports a wide range of standard platforms, including MS Windows, Linux/BSD, and macOS.
- It allows admins to configure and fire up their mail servers by just changing a few lines of code.
- Dwarf Mail Server employs the Java™ Platform Security Architecture alongside SSL/TLS for secure communication.
16. Open-Xchange Mail
Open-Xchange is a powerful and effective web collaboration suite that provides a powerful mail server for Linux enthusiasts. The software requires a paid subscription, but users can try out their community edition to see whether it fits their requirements.
The email functionalities provided by their server software include secure webmail, convenient contact management, intuitive scheduler, and a useful set of superior email protocols. All in all, Open-Xchange Mail is a suitable option for enterprises.
Features of Open-Xchange Mail
- Open-Xchange Mail allows admins to host their email servers either personally or on their dedicated clouds.
- The webmail feature provided by this mail server software is extremely robust and lives up to modern standards.
- It leverages the Dovecot IMAP server for providing superior email delivery speed and efficiency.
- Open-Xchange mobile apps allow users to manage their emails anywhere they go, anytime.
17. Cyrus IMAP server
The Cyrus IMAP server is a robust Linux mail server developed in the early 80s at the Carnegie Mellon University. It was a very advanced project of its time and proved to be a significant success. The software is now available as an open source mail server, and anybody can modify it to match their emailing needs. It offers quite a modest set of functionalities such as multiple protocol support, powerful mail filtering mechanisms, and asynchronous read/write connections.
Features of Cyrus IMAP server
- The filesystem used by this server’s mail spool is similar in layout and format to Qmail, Courier, Dovecot, etc.
- Cyrus IMAP server provides robust mail filtering using the mail filtering language Sieve.
- It allows integrated calendaring and email solutions through the CalDAV and CardDAV protocols.
- The software is still in active development, which means bug fixes and software updates are available now and then.
18. Horde WebMail
Horde WebMail is a free groupware solution that provides powerful email delivery and management capabilities for modern-day Linux users. It is a browser-based communication suite that can be used by enterprises and offers a massive set of features and modules to add-on.
Although we found it hard to set up the software at first, its convenient web-based interface makes management a breeze. Overall, the Horde mail server is a feasible solution for people looking for full-fledged mail servers.
Features of Horde WebMail
- It offers robust message filtering and searching methods with an in-built spell checker and keyboard navigation support.
- Horde WebMail allows users to download message attachments in a ZIP file and setup handy aliases.
- It uses the S/MIME and PGP tools for encrypting and signing emails conveniently.
- Users can get a conversation view of their messages directly in a thread.
19. MailerQ
MailerQ is an extremely high-performing Linux mail server that is developed for handling large-scale email requests efficiently. It is a modern-day solution that integrates some of the best practices in email management. Some of its feature set include real-time monitoring, advanced feedback processing, and secure email connections. However, the software is not free and requires a substantial fee. Thus, it will be a good solution for enterprises that are ready to pay for their service.
Features of MailerQ
- MailerQ’s robust management console offers real-time information about email delivery attempts, queues, error logs, and many more.
- It allows admins to classify the response patterns of their messages and process them based on feedback and server responses.
- MailerQ was the first mail transfer agent that employed the ARC (Authenticated Received Chain) authentication method.
- Admins can schedule future messages very conveniently through the help of pre-defined email throttle schedules.
20. Maildrop
Maildrop is a lightweight yet powerful mail delivery agent that provides free disposable e-mail addresses for web forms. It is written using the C++ programming language and thus offers extremely efficient performance. The software is in active development, and new updates will keep coming with bug fixes. This Linux mail server software receives its messages from stdin and can deliver them in both Maildir and Mbox formats. It is a useful tool for many and has diverse use.
Features of Maildrop
- Maildrop can be used anywhere where the users do not want to provide their real email addresses.
- It employs extremely powerful modern-day spam filters that eliminate most email spam effectively.
- The open source nature of this mail delivery agent allows users to modify the tool to fit their email requirements.
- It is faster than many traditional mail delivery agents due to its low resource usage.
Ending Thoughts
Mail transfer agents are usually very diverse based on their intended use, often have seemingly different features. Most full-fledged Linux mail server comes with filtering mechanisms, address book, and encryption methods alongside other required elements.
Our editors have gone over a substantial list of such email servers and outlined the 20 best Linux mail server choices for you. Hopefully, we were able to provide you the insights you were looking for from this guide. Thanks for staying with us, and don’t forget to keep coming back for additional Linux guides and how-tos.
Great list overall. But you should’ve added Dovecot
Missed the simplest yet powerfull: OpenSMTPd
Mentioning Dovecot 3 times, but not listing it… 🙁