Workplace by Facebook
Something you may not know is that they have built a suite of tools especially for collaboration on teams. Use the familiar interface of Facebook to create groups and to host live chats with your whole team.
What really sets it apart however, is the collaboration with people from other companies. If you’re partners or clients working on a project together, the teams can seamlessly chat and connect, without the messiness of email. The mobile responsiveness is also a key highlight.