Horde Groupware alternatives and similar tools

Based on the "Collaborative Software" category.
Alternatively, view Horde alternatives based on common mentions on social networks and blogs.

SOGo

5.8 9.7 L1 Horde Groupware VS SOGo

SOGo is a very fast and scalable modern collaboration suite (groupware). It offers calendaring, address book management, and a full-featured Webmail client along with resource sharing and permission handling. It also makes use of documented standards (IMAP, CalDAV, CardDAV, etc.) and thereby provides native connectivity (without plugins) to many clients such as Microsoft Outlook, Apple iCal, the iPhone, Mozilla Lightning, and a plethora of mobile devices.
EGroupware

3.8 9.9 L1 Horde Groupware VS EGroupware

Web based groupware server written in PHP, forum at https://help.egroupware.org/

The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.

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Citadel/UX

- Horde Groupware VS Citadel/UX

Collaboration suite (messaging and groupware) that is descended from the Citadel family of programs.
Kolab

- Horde Groupware VS Kolab

Another groupware suite.
Zimbra

- Horde Groupware VS Zimbra

Collaborative software suite, that includes an email server and web client.