[Outlook] Manual E2E parity validation (M365 tenant)

[Jan-Kazlouski-elastic]

Parent

Part of #4264
Blocked by: outlook_cloud feature-complete

Summary

Manual E2E parity validation on a real M365 tenant: side-by-side legacy outlook (cloud) vs outlook_cloud.

Scope

• Requires M365 test tenant + Entra app with Graph app permissions (+ optional Application Access Policy for 2–5 mailboxes)
• Checklist: all document types (mail×4, calendar, contacts, DLs, tasks, attachments×3), DLS, incremental run
• Record gaps; block GA on critical parity failures

Acceptance criteria

• Side-by-side run completed and results posted on this issue
• Critical gaps filed or fixed before release QA
• Non-critical gaps documented with follow-ups

Out of scope

• Automated live CI against M365 (nice-to-have later)