Answer:
According to the Buyer Utility Map, the U.S. Postal Service is offering the convenience utility lever during the purchase stage of the buyer experience cycle.
Step-by-step explanation:
There are six stages in buyer experience cycle: Purchase, Delivery, Use, Supplements, Maintenance and Disposal. When the US Postal Service offers a "Click-N-Ship" service they're setting it on Purchase stage of the buyer experience.
The "Click-N-Ship" service is also set on the convenience utility when its availability of a product is convenient to US Postal Service customers. There they're ensuring their customers will find convenient to buy the shipping labels.
References:
Linton, Ian. “What Are the Four Types of Business Marketing Utilities?” Small Business - Chron.com, Chron.com, 7 Mar. 2019
Kim & Mauborgne. “Buyer Utility Map: Buyer Experience Cycle: Blue Ocean Tools and Frameworks.” Blue Ocean Strategy, 2019