I hate to rain on the fun parade - but I'm a bit of an expert on the topic, having worked 20 years in the industry.
SmartPost is a FedEx Express Ground based service - where FedEx takes the package most of the delivery -but partners with the USPS to deliver the package the rest of the way.
The UPS equivalent of this is Sure Post.
For all of the USPS fans - you can thank FedEx & UPS for partnering with the USPS to help keep them in business.