Communication·Standings

Mail Server Software

Mail server software sends, receives, and stores email; the right choice depends on where it can run and how it handles mailbox access, spam, and mobile sync. Compare the platforms you need with features such as IMAP/POP3 access and high availability.

The signal score is out of 10 and reflects published information about use, a public API, documentation, open-source code, and a free tier. The API, open-source, and free-tier marks show whether those options are listed for a product.

• 34 platforms
• 2 with a public API on this page
• 24 with a free tier
• Checked 23 Sept 2026

1. #PlatformSignalPlugs inPrice
2. 1
   A

   Axigenaxigen.com

   All-in-one email, calendar, and collaboration server with a free edition and 60-day trial.

   6.4 APIOpenFree Free tier
   →
3. 2
   M

   mailcowmailcow.email

   mailcow: dockerized is an open-source groupware and email suite based on Docker.

   6.4 APIOpenFree Free tier · from €8.90/mo
   →
4. 3
   CM

   Courier Mail Servercourier-mta.org

   Free Linux mail server offering ESMTP, IMAP, POP3, webmail, and mailing lists.

   6.3 APIOpenFree Free tier
   →
5. 4
   Q

   qmailcr.yp.to

   A free mail transfer agent that queues messages and supports mailing lists.

   6.3 APIOpenFree Free tier
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6. 5
   K

   Kolabkolab.org

   Free open-source suite for email, calendars, tasks, conferencing, and shared documents.

   6.3 APIOpenFree Free tier
   →
7. 6
   M

   MailEnablemailenable.com

   Freemium Windows messaging suite providing SMTP, IMAP, POP3, webmail, and collaboration editions.

   6.3 APIOpenFree Free tier · $395 one-time
   →
8. 7
   S

   SmarterMailsmartertools.com

   An email and collaboration server with calendars, meetings, chat, and file storage.

   6.3 APIOpenFree Free tier · from $500/yr
   →
9. 8
   SM

   Stalwart Mail Serverstalwart.email

   An open-source mail and collaboration server with email, calendars, contacts, and file sharing.

   6.3 APIOpenFree Free tier · from $1.09/yr
   →
10. 9
    I

    iRedMailiredmail.org

    Open-source mail server installer for Linux and BSD, with free and paid editions.

    6.2 APIOpenFree Free tier · from $10/yr
    →
11. 10
    M

    Mailumailu.io

    Free Docker-based mail server supporting IMAP, SMTP, aliases, routing, and attachment search.

    6.2 APIOpenFree Free tier
    →
12. 11
    C

    Citadelcitadel.org

    Free collaboration server combining email, calendars, contacts, forums, messaging, and web access.

    6.2 APIOpenFree Free tier
    →
13. 12
    E

    Eximexim.org

    Exim is a mail transfer agent for hosts running Unix or Unix-like operating systems.

    6.2 APIOpenFree Free tier
    →
14. 13
    MI

    Mail-in-a-Boxmailinabox.email

    Free open-source setup that turns a cloud computer into mail, webmail, contacts, and calendar server.

    6.1 APIOpenFree Free tier
    →
15. 14
    P

    Postfixpostfix.org

    A free, open-source mail server for UNIX-like systems, with SMTP encryption and authentication.

    6.1 APIOpenFree Free tier
    →
16. 15
    M

    Modoboamodoboa.org

    An open-source, self-hosted mail server with webmail and online administration.

    6.1 APIOpenFree Free tier · from €139/yr
    →
17. 16
    H

    hMailServerhmailserver.com

    Free self-hosted server for SMTP, IMAP, POP3, webmail, spam rules, and ClamAV scanning.

    6.0 APIOpenFree Free tier
    →
18. 17
    PI

    poste.ioposte.io

    A self-hosted mail server with webmail, spam protection, and a free plan.

    6.0 APIOpenFree Free tier · from $349/yr
    →
19. 18
    ZC

    Zimbra Collaborationzimbra.com

    An email and collaboration suite with calendars, contacts, tasks, and file sharing.

    6.0 APIOpenFree Free tier
    →
20. 19
    CI

    Cyrus IMAPcyrusimap.org

    Cyrus IMAP is an email, contacts, and calendar server.

    5.9 APIOpenFree Free tier
    →
21. 20
    I

    IceWarpicewarp.com

    Paid collaboration suite combining email, messaging, meetings, files, and document editing.

    5.9 APIOpenFree From $1.35/mo
    →
22. 21
    MM

    Maddy Mail Servermaddy.email

    Free Linux mail daemon sending and receiving SMTP mail with IMAP storage and security protocols.

    5.9 APIOpenFree Free tier
    →
23. 22
    AJ

    Apache Jamesjames.apache.org

    Modular JVM mail server with SMTP, IMAP, POP3, JMAP, REST, and database storage options.

    5.9 APIOpenFree Free tier
    →
24. 23
    O

    OpenSMTPDopensmtpd.org

    A free SMTP server for sending and receiving mail between compatible systems.

    5.9 APIOpenFree Free tier
    →
25. 24
    D

    Dovecotdovecot.org

    Dovecot Community Edition is an open-source email server.

    5.8 APIOpenFree Free tier
    →
26. 25
    H

    Harakaharaka.github.io

    Free, flexible SMTP server with plugins for filtering, spam checks, and high connection volume.

    5.7 APIOpenFree Free tier
    →

Places #1, #2, #3, #4, #5 on this board are open to sponsors. Take #1 · Other ways to advertise

How to choose

Which platforms does the mail server need to run on?

Start with the environment you plan to use: options include self-hosted, Linux, web, Windows, API, and iOS.

Check a product's listed platforms against your setup before comparing price or other features.

How will people access their mailboxes?

Compare the webmail interface, IMAP/POP3 access, and mobile sync with the ways people need to read email.

IMAP and POP3 are ways for mail apps to retrieve messages from a server. Confirm which access methods a product lists.

What spam protection does the mail server include?

Compare the listed antispam tools and decide whether they fit your needs.

The board also compares mailbox limits and high availability, which can help you assess capacity and service continuity.

How should I compare price and licensing?

Check whether a product has a free plan, what its paid starting price is, and whether a free trial is available. Pricing on request means the listed price is not provided upfront.

Review the license model before choosing. If you need to read or change the code, check whether the product is open source.

How can I check whether it fits my existing setup?

Compare its listed platforms and API availability with the systems you already use. A public API can let other software connect to the mail server, but check the product details for the connections you need.

Questions

What does mail server software do?

It handles email for an organization or service, including mailbox access and message delivery. Compare webmail, IMAP/POP3 access, mobile sync, and antispam tools.

Which platforms should I look for in a mail server?

Check the platforms you plan to use, such as self-hosted, Linux, web, Windows, API, or iOS, and confirm that the product lists the ones you need.

Does mail server software include a free plan?

Free-plan availability varies. Check the product's pricing details and distinguish a free plan from a free trial.

What is IMAP/POP3 access?

IMAP and POP3 are methods that mail apps use to retrieve messages from a mail server. Check whether the server supports the access method your mail apps require.

How do I compare mail server security and reliability?

Compare the listed antispam tools and high-availability support. Check product details to see which options fit your requirements.

Some top positions on this board can be paid placements, standing where they were sold. The facts on each platform are not for sale. How we rank · Disclosure