Anyway to retrieve the email address of the User of an asset?

Is there any way to get the email address of the user of the asset? Most of our users using M365 email but they do not connect to domain nor azure AD and we need to tag the asset to the correct contact for accountability. Although we can sometimes view the Username that is logged in to that asset if they create the user profile under their own name) But it does not create a proper contact based on that anyway.