Riot : Riot allows teams to communicate across a wide range of collaboration apps. If some team members use Riot while others use IRC, Slack or Gitter, Riot ...
Zulip : Powerful slack-like open source group chat
Basecamp : Basecamp is a web-based project management tool. Its primary features are to-do lists, milestone management, forum-like messaging, file sharing, and t...
SimpleLogin : With email aliases , you can be anonymous online and protect your inbox against spams and phishing. Open-source.
Postal : Postal is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready f...
Mattermost is a self-hosted solution for bringing all your team communication to one place, and making it searchable and accessible anywhere