Downgrading E5 to E3: checklist

1. Inventory which E5 features you actually use (Defender for Endpoint P2, Defender for Office 365 P2, Defender for Identity, Defender for Cloud Apps, Purview, Entra ID P2, eDiscovery Premium, Insider Risk, Power BI Pro, Teams Phone, Audio Conferencing).
2. For each used feature, pick a replacement: a Microsoft add-on on E3, a third-party product, or accept the gap.
3. Get real quotes for quote-only products and enter them in the calculator.
4. Check your agreement (EA/CSP) for when you can reduce licenses; list prices may not match what you pay.
5. Plan the migration window for security tools so endpoints and mail are never unprotected.
6. Review compliance obligations (retention, eDiscovery, DLP) with your legal and compliance team before removing Purview features.