I discovered this service a couple of years ago while I was waiting for a rather large check to come in the mail.
Enroll in the service, and you can see what mail will be delivered to on a specific day. It also tracks packages.
https://informeddelivery.usps.com/box/pages/intro/start.action
Informed Delivery® by USPS®
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
