Azure AD B2B allows organizations to share company applications and other services/resources with external users. Before, this external user should have one of following to initiate connection with the organization who sents the B2B inivitation.
1) Azure AD Account
2) Microsoft Account
3) Google Federation ( More info : https://www.rebeladmin.com/2019/02/step-step-guide-setup-federation-google-azure-ad-b2b/ )
Email one-time passcode authentication (OTP) feature now allow B2B users to authenticate using one time passcode if they cant use one of the above methods. Once OTP is issued it is only valid for 30 minutes. If user didn’t use it with in 30 minutes, he/she need to request new OTP code for authentication. Once authenticated, session will be valid for 24 hours.
This feature is still under public preview. OTP users must use the https://myapps.microsoft.com/?tenantid=<tenant id> , https://portal.azure.com/<tenant id> or https://myapps.microsoft.com/<verified domain>.onmicrosoft.com when they authenticate. In above <tenant id> should replaced with the organization’s tenant ID. <verified domain> should replace using the default domain details.
You can find the tenant id using,
Azure Portal | Azure Active Directory | Properties | Directory ID
Let’s see how we can enable this new OTP feature.
To do that,
1) Log in to Azure portal as Global Administrator
2) Go to Azure Active Directory | Organizational relationships
3) Then go to Settings