Forum Discussion
Multi factor authentication
For external users with a live ID the user would have to enable multi-factor authentication individual for themselves at https://account.live.com/proofs/Manage. You cannot enforce it.
External Office365 users need to set it up in there own Tenant. You cannor enforce this either.
You should be able to apply MFA for external users by purchasing the Azure MFA provider from Azure. See https://azure.microsoft.com/pricing/details/multi-factor-authentication/ for pricing.
If you purchase a Per Authentication license then you can apply this for external users.
See also https://docs.microsoft.com/en-us/azure/multi-factor-authentication/multi-factor-authentication-how-it-works for more details.
You could use a parent child construction on the live id. Have the child been set up to use 2FA and hand it over to the extenal party. It is a bit far fetched but it will do the trick :)
