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Open Source Microsoft Exchange Server Alternatives

The best open source alternative to Microsoft Exchange Server is Kopano. If that doesn't suit you, our users have ranked more than 25 alternatives to Microsoft Exchange Server and 17 is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Microsoft Exchange Server are hMail Server, mailcow: dockerized, Zentyal and Zimbra Collaboration Suite.

Microsoft Exchange Server alternatives are mainly Mail Servers but may also be WebMail Providers or Calendar Apps. Filter by these if you want a narrower list of alternatives or looking for a specific functionality of Microsoft Exchange Server.
This page was last updated Jun 14, 2021
  • Windows
  • Online

Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft. It is part of the...

Learn more about Microsoft Exchange Server

  1. Kopano

    • FreemiumOpen Source
    • Mac
    • Windows
    • Linux
    • Online
    • Android
    • iPhone
    • Android Tablet
    • Windows Phone
    • iPad
    • Self-Hosted
    • Microsoft Office Outlook
    • S/MIME
    • Software as a Service (SaaS)

    Kopano puts an email, video meetings, calendaring, and file sharing solution within one single interface.

    Kopano vs Microsoft Exchange Server opinions
    Almost everyone thinks Kopano is a great alternative to Microsoft Exchange Server.
    hn1

    Kopano has scalable backend and can do full MAPI server and clientside. The Webapp and Deskapp has intuitive and modern UI/UX.

    Top positive comment  over 5 years ago
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    0
    bobsp

    Scalable, open source with a great UX and it has all the features I need

    Top positive comment  over 5 years ago
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    0
    marcski

    Stable and cheap backend, flexible frontend support, open source, in full control of your data

    Positive comment over 5 years ago
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    0

    OpenSource, better to maintain, "not Microsoft"

    Positive comment over 5 years ago
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    -1

    I tried a lot of MS alternatives, OX, Zimbra, Zentyal, but what fits most with Outlook Sync was the new Kopano, it's more flexible. You can use the web app or desktop app too.

    Positive comment over 5 years ago
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    -1
  2. hMailServer is a free e-mail server for Microsoft Windows. Its used by Internet service providers, companies, governments, schools and enthusiasts in all parts of the world.

    Almost everyone thinks hMail Server is a great alternative to Microsoft Exchange Server.


  3. mailcow: dockerized

    • FreeOpen Source
    • Linux
    • Self-Hosted

    mailcow is a mail server suite based on Dovecot, Postfix, SOGo, Rspamd and other open source software, that provides a modern Web UI for administration.

  4. Zentyal

    • Linux

    Zentyal is a native Microsoft Active Directory implementation on Linux incorporating all the network services required in a small and medium business environment: Directory & Domain Server, Mail Server, Gateway and Infrastructure Server.

    Zentyal vs Microsoft Exchange Server opinions
    Some users think Zentyal is a great alternative to Microsoft Exchange Server, some don't.

    No Exchange alternative and no support for MS Outlook Client

    Negative comment over 4 years ago
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    7

    While the comments below suggest that this is AD, not exchange replacement. It was supposed to ship with SoGo / openchange as a managed add-on. You also strangely enough can't have exchange without AD. but guests do keep on posting. Exchange is just an Add-On to AD. (It extends the schema).

    Positive comment almost 2 years ago
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    0

    They do not share any common functionality. Zentyal is an Active Directory substitute, Microsoft Exchange is a groupware E-Mail (enterprise grade) server.

    Negative comment over 2 years ago
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    -3

    Not an Exchange alternative at all. Does basic AD but that is about it. It is more of a gateway server.

    Negative comment almost 3 years ago
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    -1
  5. Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more. With the most innovative web application available today, Zimbra boosts the productivity of users on any desktop and dramatically reduces TCO compared to legacy platform vendors.

    Most users think Zimbra Collaboration Suite is a great alternative to Microsoft Exchange Server.


  6. Kolab Community

    • FreemiumOpen Source
    • Linux
    • Online
    • Self-Hosted

    Kolab is entirely Free and Open Source Software (a.k.a. FOSS), and uses Open Standards. We’ll get to why this is important to us, and hope that it is important to you thereafter.

    No screenshots yet
    Most users think Kolab Community is a great alternative to Microsoft Exchange Server.
  7. SOGo

    • FreemiumOpen Source
    • Linux
    • Online
    • Thunderbird
    • Cloudron

    SOGo is groupware server with a focus on scalability and open standards.

  8. Kolab Now

    • Online
    • Software as a Service (SaaS)
    • DAVdroid

    Kolab Now provides a suite of intuitive apps in a user friendly environment to make your day to day online comms easier, smarter and most importantly; secure.

    Kolab Now vs Microsoft Exchange Server opinions
    Some users think Kolab Now is a great alternative to Microsoft Exchange Server, some don't.

    With Microsoft no longer supporting our existing setup, this was a great alternative.

    Positive comment almost 7 years ago
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    2
  9. iRedMail

    • FreemiumOpen Source
    • Linux
    • BSD
    • Self-Hosted

    A fully fledged, free email server solution, an open source project (GPL v2).

  10. OpenChange

    • FreeOpen Source
    • Linux

    OpenChange aims to provide a portable Open Source implementation of Microsoft Exchange Server and Exchange protocols.

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Showing 10 of 17 alternatives