License the audit trail, not every seat

What you will take away

• Why Purview Audit Standard is already in your E3 with 180-day retention since October 2023.
• The three mailbox events Microsoft de-gated after Storm-0558 — and why they no longer justify E5.
• How Premium, 1-year, and the 10-year add-on actually stack, and who each tier is for.
• A worked 10,000-seat scenario showing a ~$2.39M/year gap between fleet-wide E5 and scoped Premium.
• The persona map that ties entitlements to named investigators and a 5-10% high-risk subset.