Need Alternate way to Assign Employees to Assets

Hi,

We are trying to migrate the Assets from EBS to Fusion using FBDI. While doing few assets are failing due to Invalid Email address. Due to this the assets loading is getting interrupted. We have checked the reason and identified that the email address of employees is either changing or getting masked as they want to avoid email triggering during SIT or UAT phase. In this scenario the Asset assignment to employees cannot be performed by giving Email address. We need an alternate way where we can assign the asset to employees by giving Employee number or Email address. Please