Next month, Microsoft begins the last chapter of disabling basic authentication for seven email connectivity protocols in Exchange Online. Over the last two years, the program team driving the process has collected vast amounts of data to understand how Office 365 tenants use the protocols, the affected clients, and the best way of rolling out a change of this magnitude across millions of tenants. This session explains how Microsoft organized the project, collected the data, and disabled basic authentication – and the future effect it will have on both Exchange Online and Microsoft 365.