1. Understanding Synchronization and Its Stages
Microsoft Entra Connect synchronizes identity data between on-premises AD DS and Microsoft Entra ID (Azure AD). Synchronization happens in three main stages:
Most sync errors occur in the Export stage — when Entra Connect tries to push changes to Microsoft Entra ID but encounters conflicts, invalid data, or policy violations.
2. Monitoring Sync Errors
You can view synchronization errors in:
Sync errors are updated approximately every 30 minutes, capturing data from the latest synchronization attempt.
3. Common Synchronization Error Categories
| Error Type | When It Occurs | Example Scenario |
|---|---|---|
| InvalidSoftMatch | During export when an object matches by proxy address or UPN but already has an immutableId | Duplicate proxy address or UPN across users |
| ObjectTypeMismatch | When two objects of different types share the same proxy address | A user and a group both use the same SMTP address |
| AttributeValueMustBeUnique | When two or more objects share the same unique attribute value | Duplicate UPN or proxyAddress |
| IdentityDataValidationFailed | When invalid or unsupported characters exist in attributes | Invalid UPN format |
| FederatedDomainChangeError | When changing a user’s UPN between federated domains | bob@contoso.com → bob@fabrikam.com (both federated) |
| LargeObject / ExceededAllowedLength | Attribute values exceed Entra ID limits | Too many certificates, proxy addresses, or large photos |
| AdminRoleConflict | When on-prem user matches a cloud admin account | A duplicate userPrincipalName for a Global Admin |
We’ll go through each one in depth next.
4. Error: InvalidSoftMatch
Description
When Entra Connect tries to match an on-prem object with an existing cloud object, it first uses:
If a match is found by soft matching but the existing cloud object already has an immutableId, Entra ID rejects the sync with an InvalidSoftMatch error.
In other words: Entra ID says, “I found a matching email or UPN, but it already belongs to another synced object.”
Example
Common Causes
Fix Steps
Tip: If duplicate attributes are expected due to complex migrations, enable Duplicate Attribute Resiliency (DAR) — it allows Entra ID to temporarily hold duplicate values until they’re resolved.
5. Error: ObjectTypeMismatch
Description
Occurs when two different object types (User, Group, or Contact) share the same attribute value (typically a proxyAddress).
Example
Fix Steps
6. Error: AttributeValueMustBeUnique
Description
Microsoft Entra ID requires unique values for certain attributes:
If Entra Connect attempts to sync two or more objects sharing the same value, it fails with this error.
Example
Fix Steps
Note: This error is very similar to InvalidSoftMatch but occurs when both objects are already synced, not during provisioning.
7. Error: IdentityDataValidationFailed
Description
Microsoft Entra ID enforces strict rules on attribute formats and allowed characters. If an attribute (usually the userPrincipalName) includes unsupported characters or invalid format, synchronization fails.
Example
UPN john.doe@contoso#com or john_doe (missing @domain) is invalid.
Fix Steps
8. Error: FederatedDomainChangeError
Description
Occurs when a user’s UPN suffix is changed from one federated domain to another federated domain.
Example
Bob’s UPN changes from bob@contoso.com to bob@fabrikam.com. Both contoso.com and fabrikam.com are federated with AD FS. → Microsoft Entra Connect can’t automatically change the federation trust during sync.
Fix Steps
9. Error: LargeObject / ExceededAllowedLength
Description
Occurs when attribute values exceed Entra ID’s size or count limits.
Attributes prone to this:
Limits:
Fix Steps
10. Error: AdminRoleConflict
Description
Occurs when an on-premises user object tries to sync and soft-match with a Microsoft Entra user who currently has an administrative role (like Global Administrator). For security, Entra ID doesn’t allow soft-matching to privileged accounts.
Fix Steps
11. Other Rare Errors
| Error | Cause | Fix |
|---|---|---|
| ProhibitedInUsageLocationViolation | Service not available in user’s location | Correct the user’s UsageLocation in Entra ID |
| DependencyViolation | Removing a required license before dependent service | Ensure prerequisites remain assigned |
| LicenseAssignmentAttributeConcurrencyException | Multiple license assignments processed at once | Typically self-resolves after retry |
| Duplicate Proxy Address | Two mailboxes share the same proxy address | Remove duplication in AD or Exchange |
12. Troubleshooting Tools
| Tool | Purpose |
|---|---|
| Microsoft Entra Connect Health | Centralized dashboard for sync errors, agent health, and alerts. |
| Synchronization Service Manager (miisclient.exe) | On-prem GUI tool showing each import/sync/export run and errors. |
| PowerShell | Use Get-ADSyncConnectorRunStatus, Start-ADSyncSyncCycle, and Entra cmdlets (Get-MsolUser, Get-AzureADUser) to verify object state. |
| Event Viewer | Look under Applications and Services Logs → Directory Synchronization for detailed event traces. |
13. Diagnostic Workflow
When a sync error occurs:
14. Real-World Example
Scenario: A user named Emma Clarke was deleted and recreated in AD with the same email emma@contoso.com. After re-creation, she couldn’t sign in to Microsoft 365, and the Entra Connect Health portal showed InvalidSoftMatch.
Troubleshooting:
15. Best Practices to Prevent Sync Errors
16. Exam Tips
17. Summary
Synchronization errors can interrupt sign-ins, break hybrid identity links, or create inconsistent user data. To manage them effectively:
By following a systematic troubleshooting process and enforcing attribute uniqueness, you can maintain a healthy and stable hybrid identity environment.