Kerio Connect alternatives

Kerio Connect
Kerio Connect is a commercial mail and groupware server developed by Kerio Technologies. It runs on Windows, Linux, and Mac OS X. Its features include encrypted access using SSL, anti-virus and anti-spam protection, native over-the-air handheld synchronization, webmail interface, connector for Microsoft Outlook and groupware features.
Kerio Connect alternatives are:
GMail, G Suite, Microsoft Exchange