My name is Aaron, I'm a guru here at Shopify!
Currently Shopify doesn't natively support FedEx SmartPost, but there are some shipping apps available that do support it! Here's a list of apps that support FexEx SmartPost that I've found: Integrations with FedEx Smartpost.
At the moment I am unable to confirm if we will be supporting SmartPost in the future, but I'll be more than happy to pass along this feedback to the appropriate team!
Hope that's helped! Please feel free to give us a call or start a live chat at any time, we're open 24/7 for your convenience and always happy to assist!
Aaron | Shopify Guru
Answering for the benefit for others looking for a solution to handle FedEx SmartPost.
FedEx SmartPost is a special delivery service that relies on the logistics provided by both FedEx and USPS. If you want to save money, transit time and reduce handling charges, you can use the FedEx SmartPost.
As Aaron has stated, Currently Shopify doesn't support FedEx SmartPost. You can use the FedEx Rates, Labels and Tracking app which will help you handle the FedEx SmartPost along with complete FedEx shipping. You can display live FedEx rates, print FedEx labels and also handle FedEx tracking.
Regarding Smartpost integration, i think that would take a long time, as the Shopify's focus is more towards covering international width rather domestic depth. However, you can still get Smarpost in Shopify using the Multi Carrier Shipping label app. In addition, if you are looking to adjust the cost of each service, this can be also be done in the app. Also regarding proper distinction of Ground and Ground Home Delivery, you have to atfirst get address validation enabled on your FedEx account. Once you do that, then you can use the above app that will automatically classify the address as residential or commercial.