Changes in authentication

Microsoft has announced that they will not allow SMS and voice methods to be used in multifactor authentication.  Users are expected to start using Microsoft Authenticator. 

While logging in into Outlook or Teams you could have seen an announcement that points to the limited number of access times you have using your current method. During the last allowed skipped time you are seeing information that guides you thru setting up the Authenticator App. After connecting your account into Authenticator you can be required to change the preferred authentication method in https://mysignins.microsoft.com/

You can use single Authenticator app for authenticating several different sites or services.