While using Identity Provisioning Service(IPS) to run user data sync between SuccessFactors and Identity Authentication Service(IAS) I was faced with the challenge to identify duplicate email addresses within SuccessFactors.

To check for duplicate Emails please do the following:

1. Navigate to Admin Center
2. Open Check Tool
3. Under Application select User Management
4. Here you will see User Information inside which you will see DuplicateEmailAddress check. Select this using the check box and Run Check as seen on image below

5. If an error is found you will see the results under the column named results as marked in the image below
   
6. On clicking on the result link you be presented with the impacted email addresses and the users that share them. The output will look like the below and will include the proposed solution to resolve the issue.
   

Happy to share this finding. Hope it helps you too.