Azure AD Connect Sync Fail - Duplicate Attribute Error (Attribute: UPN)

Question

We have an error occurring when syncronizing users via Azure AD Connect - Refer to attached screenshot. How do we resolve this?

Answer 1

Did you see these articles?
https://learn.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-health-diagnose-sync-e...
https://learn.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-syncservice-duplicate-...
You can also validate that your directory is in good health:
https://learn.microsoft.com/en-us/microsoft-365/enterprise/prepare-for-directory-synchronization?view...