ENCLAVE – AR2.1 Exchange Deployment Environment

1. Description of the Issue

During troubleshooting of AR2.1 Exchange services, it was discovered that the services failed to start automatically (and in some cases manually) after a system reboot. The issue persisted until specific Group Policy Object (GPO) configurations were corrected.

2. Root Cause

The problem was traced to incorrect GPO link ordering in Group Policy Management:

– The ‘Default Domain Policy’ and ‘Default Domain Controllers Policy’ GPOs were mistakenly set last in the link order.

– These policies were intended to have highest precedence (i.e., first in the link order) at the domain root and in the Domain Controllers OU, respectively.

– As a result, other GPOs—namely:

  – ‘User Pol 4 Exchange 5-22’

  – ‘AR21 – Windows Server 2016 V2R1 – DC – Computer’

  – ‘Domain User Pol Adds 04-22’

overwrote critical security settings in the ‘Default Domain Controllers Policy’.

3. Technical Details

The failure specifically affected the ‘Manage auditing and security log’ user right (SeSecurityPrivilege), located in:

Computer Configuration > Windows Settings > Security Settings > Local Policies > User Rights Assignment

– This right must include the ‘SHIP\Exchange Servers’ group to allow Exchange services to start.

– This assignment is automatically configured during Exchange installation via the ‘Default Domain Controllers Policy’.

– When this GPO is overridden by others lacking the necessary permission, Exchange services on servers like MB-002 will fail to start, as they consult the DC (e.g., DC-003) for effective policy settings during boot.

4. Resolution

– GPO link order was corrected:

  – ‘Default Domain Policy’ set to first in the domain root.

  – ‘Default Domain Controllers Policy’ set to first in the Domain Controllers OU.

– RSOP (Resultant Set of Policy) was run on DC-003, confirming correct policy inheritance and proper permissions.

– Post-correction, Exchange services started successfully upon reboot.

5. Impact

– Delayed startup and availability of Exchange services on the AR2.1 system.

– Required manual troubleshooting efforts during a critical system deployment phase.

– Risk of repeat failure in other domains if GPO link order is similarly misconfigured.

6. Lessons Learned

– GPO link order matters: Lower-priority GPOs can be unintentionally overridden by higher-link-order GPOs, even if they contain essential system configurations.

– Default policies must remain prioritized: Policies like ‘Default Domain Controllers Policy’ contain foundational security settings and must not be moved down in the GPO hierarchy.

– Use RSOP and GPResult proactively: These tools should be used during system validation to verify effective permissions, especially after GPO restructuring.

– Exchange installation modifies GPOs: Be aware that Exchange setup changes domain controller policies—post-install validation is recommended.

7. Recommendations

– Audit all domain GPO link orders to ensure proper precedence of default policies.

– Document and standardize GPO hierarchy for all deployments.

– Include GPO validation checks as part of the Exchange deployment and server hardening checklist.

– Train sysadmins and field techs on the significance of GPO link ordering and tools like RSOP.