UPS CEO Carol Tome said on a call with investors that Amazon is UPS’ largest customer, but it is not the company’s most profitable customer.

United Parcel Service Inc. shares plunged after the company projected annual revenue well below expectations, telling investors that a long-awaited rebound in demand for its parcel services won’t arrive this year and prompting it to slash its low-margin business with Amazon.

United Parcel Service forecast on Thursday downbeat 2025 revenue as it accelerates a plan to slash millions of deliveries for its largest customer, Amazon.com, a surprise move that sent shares tumbling as much as 18%.