Sources: Amazon, long the USPS' biggest customer, plans to cut packages it ships via the service by at least two-thirds this fall, when its contract expires (Esther Fung/Wall Street Journal)

Esther Fung / Wall Street Journal: Sources: Amazon, long the USPS' biggest customer, plans to cut packages it ships via the service by at least two-thirds this fall, when its contract expires   —  The e-commerce giant wants to reduce its postal volume by at least two-thirds by this fall  —  Amazon.com is planning to sharply cut …