When combined with the "Use Identity Authentication user store" option, this feature allows end-users to continue using the corporate IdP for authentication. During the authentication process, the subject name ID sent from the corporate IdP in the first response to SAP IAS - usually the user's email address or UPN - is used to verify the existence of the user's profile in the SAP IAS user store, also known as the Identity Directory. SAP IAS then retrieves the required user attributes from its own user store and forwards them to the application for further processing.