Block Legacy authentication in o365

As we have started using conditional access and MFA, we are also looking to block legacy authentication this is a recommendation by Microsoft.

Legacy authentication can bypass your CA polices, I had thought disabling MAPI and others per user would be enough, but unless you disable/block the legacy authentications your really not protecting your tenant.

Here are the links I found about setting up conditional access to block legacy authentication. I had one time found a report that would tell you who/what was still using the old authentication methods. I’m still trying to find that again. If you know please leave it in the comment below.

https://docs.microsoft.com/en-us/azure/active-directory/fundamentals/concept-fundamentals-block-legacy-authentication

https://docs.microsoft.com/en-us/azure/active-directory/conditional-access/howto-conditional-access-policy-block-legacy

https://techcommunity.microsoft.com/t5/azure-active-directory-identity/azure-ad-conditional-access-support-for-blocking-legacy-auth-is/ba-p/245417

https://docs.microsoft.com/en-us/azure/active-directory/conditional-access/block-legacy-authentication