It's not impossible. It's quite easy in fact to determine if a number is a real cell phone or not by doing an NPAC lookup to see if LNP is applicable (if so, yo

It's not impossible. It's quite easy in fact to determine if a number is a real cell phone or not by doing an NPAC lookup to see if LNP is applicable (if so, you just check the service provider type, if not, a simple check of the NANPA allocation would do). Lots of companies provide it as a service. Just most places don't check and blindly try to deliver to whatever number you provided.