The company said it has reached an agreement with its largest customer to lower volumes by 50 percent, sparking a sell-off.

Amazon decided to use third-party delivery services like the U.S. Postal Service and UPS in these ZIP codes instead of its branded trucks without informing Prime users living there of the switch ...

In recent years, Amazon has developed its own fleet of aircraft and delivery trucks. But as its business has grown, it has also needed to keep shipments flowing through other couriers like UPS.