Alternatives to Citadel for all platforms with any license

Platforms

Desktop

Web / Online

Indie / Classic

  • Kolab Community icon

    Kolab Community

    Kolab Groupware is a secure, scalable, reliable, flexible, full-featured collaboration suite.

    Open Source Linux Web / Cloud Self-Hosted

  • Zimbra Collaboration Suite icon

    Zimbra Collaboration Suite

    Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more. With the most innovative web...

    Freemium Linux Web / Cloud

  • OX Open-Xchange icon

    OX Open-Xchange

    Open-Xchange Server 6 is the most advanced Linux based Groupware solution f. Open-Xchange Server 6 is superior in the following...

    Open Source Linux Web / Cloud

  • Microsoft Exchange Server icon

    Microsoft Exchange Server

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

    Commercial Windows Web / Cloud

  • Zarafa icon

    Zarafa

    Open Source Collaboration, providing integration with your existing Linux mailserver, native mobile phone support, Outlook "Look...

    Commercial Mac Windows Linux Web / Cloud

  • hMail Server icon

    hMail Server

    hMailServer is a free e-mail server for Microsoft Windows. Its used by Internet service providers, companies, governments, schools and...

    Open Source Windows

  • MDaemon Messaging Server icon

    MDaemon Messaging Server

    MDaemon Messaging Server software for Windows can be deployed in virtual, hosted cloud or private on-premise environments. It is used...

    Commercial Windows

  • eGroupWare icon

    eGroupWare

    Egroupware is a web based software for team collaboration, central data management and CRM: email client, online calendar, contact and...

    Open Source Linux Web / Cloud

  • Atmail Email Server icon

    Atmail Email Server

    Atmail webmail system offers a webmail client, email server platform and mailserver appliance for Linux, Unix and Windows. ...

    Commercial Linux Web / Cloud

  • Expanding Communication icon

    Expanding Communication

    Turnkey Solutions for the Enterprise Cloud Installation, Configuration, and Management tools for enterprise email, collaboration...

    Commercial Linux

  • Xeams icon

    Xeams

    Xeams is a secure & powerful mail server for Windows, Linux, Solaris, MacOSX and other flavors or UNIX, which supports SMTP, POP3...

    Free Personal Mac Windows Linux BSD

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  • SmarterMail Mail Server icon

    SmarterMail Mail Server

    SmarterMail delivers Exchange-level email server software features for a fraction of the cost. With lower hardware requirements...

    Freemium Windows

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