[8_hours_ago]

Correct me if I'm wrong, but Microsoft Team doesn't currently have a self-hosted option. I hope it's in the pipeline because my company can't use an offsite IM service. It would be nice if Microsoft added support and then Slack followed. Competition is good!

[it33]

Mattermost is an open source, self-hosted Slack-alternative: https://www.mattermost.org/what-slack-might-learn-from-its-o...

[oddvar]

There is also Matrix (matrix.org), an open standard for decentralized communications. Our goal is to let all apps talk to each other - including Slack, Mattermost, and Microsoft Teams!

Check it out using any Matrix-enabled app: https://matrix.to/#/#matrix:matrix.org

[cmdrfred]

Skype can be self hosted.