ShipStation integrates with a few USPS partner carriers where a third party carrier, such as UPS or FedEx, picks up the package then transfers it to USPS who makes the final delivery.
USPS Partner Carriers:
- UPS Mail Innovations
- FedEx SmartPost
- DHL Global Mail
For each of these services, both the partner carrier and USPS provide a separate tracking number. The tracking number on the label is the USPS tracking number, and the tracking number within the ShipStation Shipments tab is the carrier tracking number.
FedEx currently shows tracking on their carrier tracking page from pickup to delivery for SmartPost services.