You need to pass the inspection before signing. If the courier insists that you sign first, then you sign it and put it where he can't get it without your permission. If it passes the inspection, give it to him. If you fail, don't give it to him or cross the front line. If there is a problem with the goods, you can call the seller at that time to ask. If it can't be solved at that time, you won't sign for the courier or receive the goods.