Service / Cloud Security / Microsoft 365

Mimecast to Defender Migration

Consolidate your security stack, reduce licensing costs and simplify operations. We deliver a zero-disruption migration from Mimecast to Microsoft Defender for Office 365 with policy parity and a controlled MX cutover.

The problem: redundant spend & split signals

Many organisations licensed for Microsoft 365 E5 (or E3 + Security) already own advanced mail protection. Running Mimecast in parallel adds spend, fragments signal across portals and slows response. The barrier is risk: ensuring equivalent protection and a safe switch-over.

Our phased, proven approach

01

Discover & Audit

Deep-dive of Mimecast policies (impersonation, attachment sandbox, URL rewrite, DLP, TTP), mail flow and exceptions. Evidence pack created.

02

Design & Configure

Best-practice build in Defender for Office 365 mapped to Secure Score: anti-phishing, Safe Links/Attachments, auth (SPF/DKIM/DMARC), transport rules and user submissions.

03

Pilot & Validate

Pilot cohort with side-by-side telemetry, tuning, false-positive review and end-user comms. Archive migration plan prepared where applicable.

04

Cutover & Hypercare

After-hours MX change, routing verification, rapid rollback plan documented (and rarely needed). Hypercare with daily checks and tuning.

Why move to Defender?

  • Cost savings: Remove redundant licensing and maximise your Microsoft 365 investment.
  • Unified security: Integrated signals across Defender, Entra ID, Purview and Sentinel.
  • Simpler ops: One admin centre, consistent policy model and automated investigation & response.
  • Modern features: Advanced phishing, attack simulation training and AIR workflows.

What you’ll get

  • Config blueprint: Documented policy mappings (Mimecast → Defender) and rationale.
  • Change & comms pack: Stakeholder plan, end-user notice templates, support cues.
  • Archive strategy options: Retain, export, or migrate—with compliance considerations.
  • Post-cutover tuning: KPIs, Secure Score deltas and agreed thresholds for noise vs. catch-rate.

Ready to consolidate & save?

We’ll quantify savings, map your policies and run a controlled cutover—so users only notice fewer portals.

Get Your Migration Plan