https://mattermost.com/ is a flexible messaging platform that enables secure team collaboration
https://etherpad.org/ is a highly customizable online editor providing collaborative editing in really real-time .
https://weblate.org: web-based continuous localization
http://www.postfix.org/ is Wietse Venema’s mail server that started life at IBM research as an alternative to the widely-used Sendmail program.
https://nextcloud.com/ self-hosted productivity platform that keeps you in control.
https://icinga.com/ monitors availability and performance, gives you simple access to relevant data and raises alerts to keep you in the loop.
https://wazuh.com/ is a security monitoring solution for threat detection, integrity monitoring, incident response and compliance.
GitLab is a web-based DevOps lifecycle tool that provides a Git-repository manager providing wiki, issue-tracking and continuous integration/continuous deployment pipeline features