Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
Frontline HCM (Aesop Online) - Frontline HCM (Aesop Online) is the software that is used to increase the outcome and performance of the students by optimizing and managing the activities of the teachers and other employees of the school.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
APS - We Make Payroll and HR Easier
mailcow - An open source mailserver suite.
OnePoint Human Capital Management - OnePoint Human Capital Management is a web-based workforce management solution with payroll outsourcing & benefits/ACA capabilities