OwnDrive is easy to use free online storage service for businesses, professionals, and individuals to store, backup, collaborate and share files with others.

Kolab is a free and open source groupware suite.

Baïkal is a Cal and CardDAV server, based on sabre/dav, that includes an administrative interface for easy management.

Memotoo sync all your contacts from Gmail, Facebook, phone, Thunderbird, Outlook, etc in a single address book.

Kolab Now is a web-based email and groupware service, based completely on free and open-source software.

SOGo (Scalable OpenGroupware.org) is an open source collaborative software (groupware) server with a focus on simplicity and scalability.

Kopano is an open-source groupware application suite originally based on Zarafa.

Mailfence is a web-based email service that offers OpenPGP based end-to-end encryption and digital signatures.