Microsoft Defender for Office 365 vs Mimecast

Microsoft Defender for Office 365 and Mimecast are both cloud email security solutions. Microsoft Defender for Office 365 microsoft's native email security for Microsoft 365 with XDR integration, while Mimecast cloud email security platform with threat protection, archiving, and continuity. The best choice depends on your organization's size, technical requirements, and budget.

Updated Feb 2026
How we compare:This comparison is based on official documentation, public pricing, community discussions, and aggregated user feedback, not hands-on testing by our team. We organize what real users and practitioners are saying across the web.

The Bottom Line

Choose Microsoft Defender for Office 365 if deep native integration with Microsoft 365 and Defender XDR ecosystem is your priority and microsoft 365-centric organizations wanting native email security with XDR integration and cost efficiency through E5 licensing. Choose Mimecast if email continuity keeps mail flowing during outages — unique differentiator matters most and mid-to-large enterprises wanting a unified email security, archiving, and continuity platform with strong API integrations.

Choose Microsoft Defender for Office 365 if:

  • You value deep native integration with Microsoft 365 and Defender XDR ecosystem
  • You value included in Microsoft 365 E5 — significant cost savings for E5 customers
  • You value automated investigation and response reduces analyst workload
  • You want to avoid detection efficacy slightly behind Proofpoint for advanced threats
  • You want to avoid email archiving search performance can be slow on large datasets

Choose Mimecast if:

  • You value email continuity keeps mail flowing during outages — unique differentiator
  • You value strong impersonation and brand protection capabilities
  • You value unified platform covering security, archiving, and continuity
  • You want to avoid only protects Microsoft 365 — does not support Google Workspace or other platforms
  • You want to avoid detection efficacy for advanced threats historically behind Proofpoint and Mimecast

Feature Comparison

FeatureMicrosoft Defender for Office 365Mimecast
PricingPlan 1 from $2/user/month / Plan 2 from $5/user/month / included in E5Custom pricing / per-user licensing
Pricing ModelPer-user subscription (bundled with Microsoft 365 E5)Per-user subscription
Open SourceNoNo
DeploymentCloudCloud
Best ForMicrosoft 365-centric organizations wanting native email security with XDR integration and cost efficiency through E5 licensingMid-to-large enterprises wanting a unified email security, archiving, and continuity platform with strong API integrations
Safe Links (URL detonation and rewrit...SupportedNot available
Safe Attachments (sandbox analysis)SupportedNot available
Anti-phishing with impersonation prot...SupportedNot available

Sources

Related

Microsoft Defender for Office 365 AlternativesMimecast AlternativesMicrosoft Defender for Office 365 OverviewMimecast Overview