Start with the information you need to protect. Assign an owner and define who should be able to use it before choosing additional encryption controls.
Map information before controls
Begin with a small inventory of high-value libraries: contracts, personnel records, financial forecasts, and customer documents. Record the business owner, intended readers, external collaborators, and the impact of accidental disclosure.
Use that inventory to distinguish routine internal information from material that requires protection after download. A single rule for every document can create unnecessary friction and encourage workarounds.
Understand the protection layers
SharePoint Online encrypts data in transit and at rest. These service protections do not replace access decisions or prevent an authorized user from sharing information inappropriately.
File-level sensitivity labels can add persistent protection to supported documents. Treat file protection and site permissions as complementary controls, and check the supported file types and collaboration behavior before rollout.
Make ownership operational
Ask each library owner to approve a short handling standard: who can access the content, when external access is appropriate, and who reviews exceptions. Keep the standard close to the work so staff can find it.
Pilot with a representative business team. Include browser editing, desktop applications, downloads, guest collaboration, and an employee leaving the organization in your test scenarios.
Review the outcome
Schedule a recurring review of membership, label choices, and support incidents. Investigate repeated requests to remove protection: they may reveal an overly broad policy or a missing approved workflow.
Keep evidence of the tests and record who owns unresolved exceptions. Expand the policy only after the pilot demonstrates that both protection and everyday collaboration work.
Further reading
Validate configuration choices against Microsoft’s current documentation and your tenant’s available licenses.
Microsoft: Data encryption in OneDrive and SharePoint ↗Microsoft: Sensitivity labels for SharePoint and OneDrive files ↗