Hey, thanks! I don't know much about antitrust, so this is likely to be a dumb question; Why is messaging a new/different market for Microsoft regarding O365?

Hey, thanks! I don't know much about antitrust, so this is likely to be a dumb question; Why is messaging a new/different market for Microsoft regarding O365? Microsoft has been including business-targeted messaging/collab tools in O365 for years. Skype for Business preceded Slack, let alone Office Communicator or Linc, not to mention Outlook.