How to Find Guest Accounts Blocked by the Azure AD B2B Collaboration Policy

Blocking domains through the Azure AD B2B collaboration policy stops group owners adding new guest accounts from certain domains. It does nothing about existing guests from those domains. Fortunately, it’s relatively easy to check the guest membership of Groups and Teams to find guests from the blocked domains. And once you know those problem guests, you can decide what to do up to and including removing guest accounts from the tenant.