Received 5 or 6 of these over the past month or so. On these, the date was usually about 10 days earlier. Of course you're right that the USPS doesn't have your email address. Look at the address of the sender. They've been from all over the world. Also should show it to your local postmaster. I would guess the USPS will investigate it. Got something similar from the "IRS" a while back. I reported it and an agent was at my office in less than an hour.