Microsoft 365 E5 shops consolidating (Defender for O365 wins), modern AI-behavioral leadership buyers (Abnormal wins), or buyers wanting transparent pricing.
Mid-market and enterprise buyers (500-50,000 employees) wanting an integrated bundle of email security + continuity + archive + awareness training under a single vendor, particularly in the UK and EU.
Why we say this
Editorial pulled these weaknesses from Mimecast’s product card in our Top 10 Email Security Software for 2026:
- ! PE-driven price escalation aggressive (10-18% annual increases reported under Permira)
- ! Behavioral AI lags Abnormal materially
- ! Platform UX dated; multi-console workflow
- ! Microsoft Defender for O365 erodes installed base on every M365 E5 renewal
- ! Customer support quality declined post-2022 take-private
- ! Innovation pace slower than modern AI-behavioral challengers
If Mimecast is wrong for you, consider these instead
Same Email Security Software category, different best-fit buyer.
Best for
Enterprises (1,000-100,000+ employees) on Microsoft 365 or Google Workspace adding an AI-behavioral overlay on top of Defender for O365 or a legacy SEG to catch BEC, ATO, and vendor email compromise.
See full profile →Best for
Large regulated enterprises (financial services, healthcare, federal) wanting a mature SEG with the broadest archive / DLP / compliance bundle and willing to pay premium pricing under PE ownership.
See full profile →Best for
Any organization on Microsoft 365 E5 (essentially standard at zero marginal cost), or M365 E3 / Business Premium organizations adding Defender for O365 Plan 2 standalone.
See full profile →Related editorial
Last updated 2026-05-09. Editorial verdict based on the published Top 10 Email Security Software for 2026 ranking. Disagree? Tell us.