Webform in an app with a known and wanted pre populated email validation

Hello,

I have a a simple acknowledgement webform that needs a signature and thats it. The webform is embedded into a website and when its signed it needs to be a specific company email for another part of the app to work properly (azure logic app - When document signed => do things). In app, the email wanted is a variable. Unfortunatly, sometimes the users will validate with non company emails. Can the validation portion of a WebForm be prepopulated with a variable from a webapp? We are using the IFrame embed.