Setting up and using Microsoft MFA becomes mandatory for guest users (Azure AD guest users) on most Office365 applications.
Guest users will be presented with the built-in wizard to set up and use Microsoft MFA for the account on the next login to Office365 applications.
This applies to the following situations:
– if a guest user has been granted or will be granted access to a Teams group or full SharePoint site
– when a file or folder from OneDrive and or SharePoint is shared or has been shared directly with a guest user
This does not apply to participating in Teams meetings.