Mail Shark employs a full-time official USPS agent that verifies all our mail before it is delivered to the post office. We would be happy to provide you with postal receipts upon request. In addition, if you are doing a saturation mailing program, you can log on to our web-based system and see exactly where your pieces are being mailed and the exact quantity that is being sent. Once the phone calls start coming in, you will definitely know where and when your pieces are being delivered!