You will be shown how IT managers can harden their M365 tenant and thus protect the data stored in it. To this end, all important Microsoft 365 services for security and external collaboration are presented and how these services can be configured according to best practices. Furthermore, a holistic zero-trust approach to securing Microsoft 365 usage will be presented in order to protect data and systems from third-party access. The seminar is rounded off by a guide to setting up a protected environment on mobile devices for the use of Microsoft 365 data.