External sharing is not one setting. It is a collaboration risk model across tenant settings, site settings, link types, identity, data sensitivity, ownership and lifecycle. This interactive policy builder helps Microsoft 365 admins, SharePoint admins and security teams design practical sharing controls that enable collaboration without creating uncontrolled data exposure. Includes a 10-input sharing risk scoring engine, tenant-level and site-level sharing recommendations, link type decision framework, guest access lifecycle with Entra B2B, anonymous link guidance, sensitivity labels and DLP integration, Copilot oversharing remediation, Conditional Access for external users, rollout phases, and 16 common sharing mistakes from real tenants.

Every Zero Trust deployment has gaps. The slide decks do not mention them. The vendor assessments gloss over them. But they are there, in every tenant. This article is the honest assessment: the BYOD browser gap where unmanaged browsers bypass app protection entirely, legacy apps that cannot do modern auth and sit outside the CA perimeter, printers and IoT devices that cannot authenticate, third-party VPNs that mask device posture, service accounts that cannot do MFA, guest users with unknown MFA quality and no device compliance, a gap severity matrix, and a practical gap assessment checklist. Zero Trust does not fail because of technology. It fails because of compromises made for usability, legacy systems, and operational reality.