Slack - A messaging app for teams who see through the Earth!
chatmego - Sign in to chatmego or create an account - start connecting new friends with me, share photos, videos, messages, a story, and vote with me
Mattermost - Mattermost is an open source alternative to Slack.
Loop Email - Emailing for teams: Organize your Inbox into channels 💌
Project Sonoma - The one-stop app for deskless workers by Microsoft
Jive Chime - Real-time messaging for your team