A1: Yes, you can reference them by the carrier tracking number (although you could not void/modify a shipment that wasn't created by your carrier account). A2:

A1: Yes, you can reference them by the carrier tracking number (although you could not void/modify a shipment that wasn't created by your carrier account). A2: Do those have a tracking number pre-printed? If so, yes. It will also work with a UPS InfoNotice or Waybill #. A3: Yes! We have "best-effort" functionality, it will be expanded to add more complex statements, but we currently have "Send best price from X to Y within N days." A4: Yes, if you rate is lower than ours and you are over a certain shipping threshold.