One-time passcode authentication for B2B guest users - Microsoft Entra External ID

How to use Email one-time passcode to authenticate B2B guest users without the need for a Microsoft account.

Sign-in to Microsoft Entra ID with email as an alternate login ID

External Identity in Azure AD and B2X user flows

New Azure AD External Identities Features

Govern access for external users in entitlement management

Azure AD B2B Collaboration Archives - Office 365 for IT Pros

One-time passcode authentication for Azure AD B2B Guest Users

B2B collaboration FAQs - Microsoft Entra External ID

Tutorial - multifactor authentication for B2B - Microsoft Entra

The Attackers Guide to Azure AD Conditional Access – Daniel

Troubleshooting B2B collaboration - Microsoft Entra External ID

Govern access for external users in entitlement management