Thank you. I didn't know of this distinction. I poked around a little and found something at the EFF website[1].

Now my next question is can someone force the third party to give up the information without a warrant? I know they most likely will just comply. However, just for completeness, can a company like FedEx say that they require a warrant before opening packages?

[1] https://ssd.eff.org/your-computer/govt/privacy