Office 365 Additional Security, Require MFA to Domain Join Devices in Azure Active Directory
How to enable the feature to prompt for Multi Factor Authentication when joining a device to an Azure Active Directory domain. We would also like to limit the number of devices a user can have to 5.
Start in Azure Active Directory Admin Center
Select Azure Active Directory > Devices
Under Devices click “Device Settings”
Now you can set the max number of devices per user and enforce MFA to join devices
