Collaboration between Azure Active Directory tenants typically involves Azure AD Guest accounts. After a few years, the proliferation of ‘Guest’ accounts usually becomes a focus, especially for larger tenants. As Azure AD has matured the meta data associated with accounts, along with Microsoft Graph improvements is making it easier to define and locate stale Azure AD B2B Guest Accounts.… keep reading
Update: Oct 30 '18 Also see this post that adds support for Microsoft's updates to the Microsoft Graph to include additional information about Azure AD B2B Guest users.
Earlier this year Microsoft released the Microsoft Identity Manager Azure AD B2B Management Agent.… keep reading