We all know that the guest accounts created by Azure B2B Collaboration for apps like Teams, Planner, and Groups are a great way to share information with external people. You control what guests do in your tenant, but it's not as easy to know what your tenant users do as guests in other tenants. You could ask them... and that's it. Maybe Microsoft should come up with a way for tenant administrators and compliance officers to know what users do when they visit other Office 365 tenants.
https://petri.com/problem-guest-users-outside-tenant
