Enable Authentications for apps for external users

[A_Sidhu]

Hello,

I have enabled SSO for an application using SAML confg. Also enabled MFA for the users i=within the organization. However, I would also like to set-up MFA for the external users who are in AD as "mail user" to access the apps.

Could anyone please guide on these steps?

Thank you for your time.

[#2]

Hmm, I am not sure if it is supported, as they are more like contacts than actual users.

Can you force MFA on them from the M365 Admin centre?

https://account.cloud.ppi.net/knowledgebase/10/Set-up-multi-factor-authentication-for-Office-365-use...

Other than that the only thing that is coming to mind is to either give them a proper active directory account or invite them as external/guest users and configure MFA that way:
https://docs.microsoft.com/en-us/azure/active-directory/external-identities/b2b-tutorial-require-mfa