The United States Post Offices has a great free service called “Informed Delivery”.
“Digitally preview your mail and manage your packages scheduled to arrive soon! Informed Delivery allows you to view greyscale images of the exterior, address side of letter-sized mailpieces and track packages in one convenient location.** Images are only provided for letter-sized mailpieces that are processed through USPS’ automated equipment.”
Click here to check it out / sign up!