Kolab Now
Commercial
Kolab Now is a web-based email and groupware service, based completely on free and open-source software.
SOGo
Open Source
SOGo (Scalable OpenGroupware.org) is an open source collaborative software (groupware) server with a focus on simplicity and scalability.
Kopano
Open Source
Kopano is an open-source groupware application suite originally based on Zarafa.
OX Open-Xchange
Open Source
OX Open-Xchange is a web-based communication, collaboration and office productivity software.
Kolab Community
Open Source
Kolab is a free and open source groupware suite.
Zimbra Collaboration Suite
Freemium
Zimbra offers an open source email platform for the enterprise.
Zarafa
Commercial
Zarafa is an open-source groupware application.
Compare Microsoft Exchange Server with alternatives
Compare Kolab Now and Microsoft Exchange Server and decide which is most suitable for you.
Compare Kolab Community and Microsoft Exchange Server and decide which is most suitable for you.
Compare SOGo and Microsoft Exchange Server and decide which is most suitable for you.
Compare Zimbra Collaboration Suite and Microsoft Exchange Server and decide which is most suitable for you.
Compare Kopano and Microsoft Exchange Server and decide which is most suitable for you.
Compare Zarafa and Microsoft Exchange Server and decide which is most suitable for you.
Compare OX Open-Xchange and Microsoft Exchange Server and decide which is most suitable for you.