If you're shipping anything expensive you should not use smartpost, USPS, or mail innovations. Making a lost package claim won't go anywhere if there was a handoff to a different carrier, if it was straight fedex home delivery it's fast and easy.
Smartpost usually works fine though, and a few years ago when I was in shipping Fedex was the #2 USPS customer because of it. UPS does the same thing called Mail Innovations, so beware.