Simple definition
Cross-tenant access settings control inbound and outbound B2B collaboration and direct connect between Microsoft Entra organizations.
Purpose and use
Entra cross-tenant access settings govern collaboration and access involving identities from multiple organizations.
How does it work?
They distinguish inbound and outbound access and optional trust in selected partner MFA or device claims.
Example and verification
For denied external access, inspect settings on both organizations and logs identifying the actual resource and identity.
Points to watch
Allowing a tenant does not automatically create every required account or permission. Application and Conditional Access policies still apply.
In short
Assess controls in both directions and alongside the collaboration mechanisms actually in use.