CMMC Ready — CMMC Level 2
82% NIST 800-171 coverage. 2 control gaps identified.
CMMC Status
CMMC Ready
Target Level
Level 2
NIST Coverage
82%
Mimecast Government
by Mimecast
Overview
Mimecast Government by Mimecast is an email & messaging solution with FedRAMP authorization targeting CMMC Level 2 compliance. It provides 82% coverage of NIST 800-171 controls for defense contractors handling CUI.
What This Means for Defense Contractors
Mimecast Government meets the architectural requirements for CMMC Level 2. However, CMMC compliance depends on your entire system boundary — not just individual tools. There are 2 NIST 800-171 control gaps that need remediation before assessment. Defense contractors using Mimecast Government should verify that their System Security Plan (SSP) documents how this tool fits within their authorization boundary.
NIST 800-171 Coverage
Control Gaps
Using Mimecast Government without addressing these NIST 800-171 controls may result in findings during a CMMC assessment:
Strengths
Using Mimecast Government in a CMMC Environment
For defense contractors already using Mimecast Government, the path to CMMC compliance involves documenting the tool in your System Security Plan (SSP), ensuring proper access controls are configured, and validating that Mimecast Government's security controls align with your authorization boundary. With 82% NIST 800-171 coverage, Mimecast Government provides a strong compliance foundation, though the 2 remaining control gaps will need compensating controls or supplementary tools.
CMMC-Ready Email & Messaging Alternatives
CMMC Compliance Analysis for Mimecast Government
Mimecast Government demonstrates strong CMMC Level 2 readiness with its FedRAMP authorization and dedicated government infrastructure, making it suitable for inclusion within the CMMC authorization boundary. The platform excels in Access Control (3.1) with robust role-based permissions, Identification and Authentication (3.5) through MFA integration, and System and Communications Protection (3.13) via end-to-end encryption. Its audit logging capabilities strongly support Audit and Accountability (3.3) requirements. However, critical gaps exist in Media Protection controls 3.8.1 (media storage protection) and 3.8.3 (media sanitization), which directly impact CUI handling workflows when contractors archive or export email data containing sensitive information. During a C3PAO assessment, evaluators will scrutinize how email attachments and messages containing CUI are protected during storage, backup, and disposal processes. The dedicated government data centers and SIEM integration provide strong foundational security, but assessors will require documented compensating controls for media protection gaps. Compared to competitors like Microsoft 365 GCC High or Google Workspace for Government, Mimecast Government offers superior email security features but requires additional controls for complete CMMC compliance. The 82% NIST coverage is respectable, positioning it as a viable solution with manageable remediation requirements for defense contractors seeking CMMC certification.
Configuration Guide
Configure Mimecast Government with maximum security settings: enable message-level encryption for all CUI communications, implement data loss prevention policies targeting CUI markings, and configure retention policies aligned with NARA guidelines. Document compensating controls in the SSP for gaps 3.8.1 and 3.8.3, including third-party secure media destruction services and encrypted backup validation procedures. Implement continuous monitoring through SIEM integration, configuring alerts for unauthorized access attempts, privilege escalations, and data exfiltration indicators. Establish quarterly access reviews and monthly security configuration validation. Timeline: 4-6 weeks for initial configuration, 2-3 weeks for compensating control documentation, and ongoing monthly maintenance cycles. Prepare evidence packages including: configuration screenshots, audit logs demonstrating control effectiveness, documented procedures for media sanitization, and MFA implementation records. Conduct tabletop exercises simulating CUI breach scenarios to validate incident response procedures. Deploy email classification banners and user training on CUI handling within the email environment. Document all configuration changes in the change management system and update security control assessments quarterly to maintain assessment readiness.
Configuration Checklist
- 1ISSO: Configure message-level encryption policies for all emails containing CUI markings within Mimecast console
- 2Sysadmin: Enable multi-factor authentication for all Mimecast Government user accounts per NIST 800-171 3.5.3
- 3ISSO: Document compensating controls for NIST 3.8.1 and 3.8.3 in System Security Plan Section 13
- 4Sysadmin: Implement data loss prevention rules targeting CUI classification markings and keywords
- 5ISSO: Establish quarterly access control reviews documenting role assignments per NIST 800-171 3.1.1
- 6Contracts: Execute agreements with certified media destruction vendor for email archive disposal
- 7Sysadmin: Configure SIEM integration for real-time monitoring of email security events
- 8ISSO: Develop incident response procedures specific to email-based CUI breaches for POA&M tracking
- 9C3PAO: Prepare audit evidence packages including configuration screenshots and access logs
- 10ISSO: Conduct monthly compliance validation reviews and update continuous monitoring dashboard
Estimated Compliance Cost
Initial setup and remediation costs range from $15,000-$25,000, including professional services for configuration optimization, compensating control documentation, and staff training. Annual ongoing costs typically range $8,000-$12,000 covering quarterly compliance reviews, security configuration validation, and user training updates. Continuous monitoring implementation requires $5,000-$8,000 annually for SIEM integration and automated compliance reporting tools. Total timeline spans 6-10 weeks for initial compliance readiness, with ongoing monthly maintenance requiring 4-6 hours of ISSO time. Additional costs may include third-party media destruction services ($2,000-$3,000 annually) and specialized training for email security administrators ($1,500-$2,500 per person). Budget for annual penetration testing focused on email security controls ($5,000-$8,000) and potential consultant support during C3PAO assessment preparation ($3,000-$5,000).
Compliance Cross-References
Mimecast Government directly supports DFARS 252.204-7012 requirements through FedRAMP authorization and adequate security controls implementation, while its encryption capabilities address DFARS 252.204-7021 CUI protection mandates. The solution covers 13 of 17 NIST 800-171 control families, with strong performance in Access Control (AC), Audit and Accountability (AU), and System and Communications Protection (SC) domains critical for CMMC Level 2. Identified gaps in Media Protection (MP) family controls 3.8.1 and 3.8.3 require documented compensating controls but don't prevent CMMC certification. The FedRAMP Moderate authorization provides baseline assurance for CMMC assessors, as FedRAMP controls overlap significantly with NIST 800-171 requirements. CMMC assessment domains of Asset Management, Access Control, and Data Protection are well-supported, while Configuration Management and Recovery domains may require additional documentation. The solution's government cloud infrastructure satisfies CMMC scoping requirements for cloud service providers, eliminating concerns about CUI data location and foreign ownership that could complicate assessment boundary definitions.
Frequently Asked Questions
Is Mimecast Government CMMC compliant?
Mimecast Government meets CMMC Level 2 requirements with 82% NIST 800-171 control coverage.
What NIST 800-171 controls does Mimecast Government cover?
Mimecast Government covers 82% of the 110 NIST 800-171 controls, with 2 gaps primarily in 3.8.1 and 3.8.3 control families.
What are the CMMC compliance gaps for Mimecast Government?
The primary gaps are in controls 3.8.1, 3.8.3. These require supplementary tools or process controls to achieve full CMMC Level 2 compliance.
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