3 ms·

But how do they validate the request came from the sender?

• mh- 3y ago
  They probably only allow it for business customers. In which case there's a shipper account associated with the tracking number and they have online access to view/manage all outgoing parcels/deliveries. This used to be called Quantum View; a quick google suggests it still is.
• pests 3y ago
  You create an account if you are sending online. The shipment is linked to that account. Then when you ship in-person you can add those shipments to your online account via some id on the shipping receipt last time I checked.