Kerio Connect (originally called Kerio MailServer) was one of the first groupware solutions to appear way back in 2001. Unfortunately, Kerio Connect still centers around email as the primary means of internal collaboration, while more and more people use social networks, instant messaging, video conferencing and online file sharing for work, reserving email for client communications. If you are looking for a free modern Kerio Connect alternative, available in cloud or as a self-hosted solution, with native mobile apps for iOS and Android, take a look at Bitrix24.
* Please note that the information may have changed since the publication. For current prices and features please visit Bitrix24 pricing page.