The App_Config/Include/S4S.config file contains the S4S.UniqueKeyProperty setting. The setting defines the Salesforce contact field which will be used as the unique key for the represented Sitecore users. Any string field can be used as the unique key. This means the following:

 

Note: If you leave the setting empty, then the SitecoreUsername__c field will be used as the unique key. Additionally remember that if your org has a namespace prefix this will need to be added to the field. 

Next Step

Configuring UniqueKeyCaseSensitiveProperty (Optional)

Steps