Office 365 makes it easy to collaborate with external users through Office 365 Groups and Teams, both of which use Azure B2B Collaboration. In fact, collaboration is so easy that users might be carried away and share with all and sundry, including your competitors. Which is why it’s nice to have a policy to control sharing with certain domains that works for applications like Groups, Teams, and Planner.
https://www.petri.com/azure-active-directory-external-collaboration-policy
