Microsoft spent the first of September restoring 365 after an outage that took down Exchange Online, Teams, SharePoint, OneDrive and Copilot at the same time. Mail flow came back before search did. Users kept hitting failures across several services well after the headline recovery. The cause was a configuration problem in a core authentication component shared by all of them. That single sentence is the entire lesson, and it’s worth sitting with rather than filing under bad day at the office.