This type of thing has been happening for several years now. All allege that a package couldn't be delivered. It's called "phishing". The scammers are hoping you'll bite and give out your personal information so that they can steal from you.
Post office tracking is initiated by the package sender based on a tracking number assigned when the mail charges for the package is paid. In every case where I have used mail tracking, I had to contact the post office and enter that number to get information.
I rarely use Fed-ex or UPS, but I imagine their tracking works similarly.