By default, ANY user from ANY external Microsoft Entra tenant can be added as a guest in your tenant. Combined with permissive Teams settings, this lets attackers in any tenant DM and share files with your users — bypassing email security entirely.
A scan reports where your tenant stands on this check — pass, fail with a step-by-step fix, or not applicable if your licensing doesn’t include the feature. When Tenant Strike can’t read a setting with read-only access, it says unverified and gives you a one-command way to confirm it yourself — it never guesses.
Related Sharing & Collaboration checks
Check your own tenant
Is your tenant covered on "restrict cross-tenant collaboration"?
One read-only scan answers it — this check and every other one in the catalog, each with a plain-English fix. 7-day Pro trial, no credit card.