Unable to update this object because the following attributes associated with this object have values that may already be associated with another object in your local directory services: [ProxyAddresses smtp:[email protected];]. Correct or remove the duplicate values in your local directory. Please refer to http://support.microsoft.com/kb/2647098 for more information on identifying objects with duplicate attribute values.

Tracking Id: 959f1a9d-f532-412c-be43-4e8873276255
ExtraErrorDetails:
\{“Key”:”AttributeConflictName”,”Value”:[“ProxyAddresses”]},{“Key”:”AttributeConflictValues”,”Value”:[“smtp:[email protected]”]}]

The Microsoft Online Email Routing Address (MOERA) has the format <domain>.onmicrosoft.com and is a specific address for routing emails towards Exchange Online.

How the proxyAddresses attribute is populated in Azure AD

 Since the MOERA is constructed from the person’s userPrincipalName (UPN) attribute in Active Directory and is automatically assigned to the cloud account during the initial sync and once created, it cannot be modified or removed in Microsoft 365.

Fix

• Move the user to a non-sync OU in AD and remove it from the sync scope. In case you are using a custom attribute for determination if a user object is synched via Azure AD Connect or not, it is sufficient to remove this attribute and therefor exclude the user from Azure AD Connect sync
• Force the delta sync
• User is now soft deleted in the cloud. Go to the Azure portal / users / deleted users and restore the user from here.
• User is now a cloud-only object, and you can proceed to the exchange online admin center, in order to manually edit the MOERA.
• After you finish editing the email aliases as desired, put the AD user back to the sync scope and force a delta sync.