United Parcel Service Inc. expects to cut 20,000 jobs this year and close dozens of facilities as it dramatically reduces shipments for e-commerce giant Amazon.com Inc.

The reduction in its operational workforce — a group that includes delivery drivers and package handlers — is part of a network overhaul in response to expected “lower volumes from our largest customer,” UPS said Tuesday in a statement that also detailed first-quarter results. The Atlanta-based company will shutter 73 leased and owned buildings by the end of June and said it may identify additional facilities for closure.