The U.S. Postal Service quietly has built up 21 million subscribers for its Informed Delivery program, which allows customers to see each day’s mail before the contents are delivered.

The service is free. Customers simply register at and in return receive a daily digital preview of bills, checks, letters and other correspondence, said Naddia Dhalai, Ohio spokeswoman for the postal service.

“We want everybody in the country to start using it,” Dhalai said. “That’s our goal.”

High-tech scanners capture images of the exterior address side of the letter – but not its contents – and the scans may be viewed via email or an online dashboard accessible from a smartphone, computer or other electronic device, according to the USPS website.

Notification begins about three days after signing up, the website said.

The service was launched in 2017 as a convenience for postal-service customers, Dhalai said.

“It’s just a service to update our customers what’s coming through,” she said. “Sometimes we expect things that are coming, but we’re just waiting for them.”

Customers also may sign up for USPS Tracking to provide delivery instructions, manage notifications and schedule redelivery of incoming packages.

Though the holiday season has passed, Informed Delivery is useful year-round, Dhalai said, particularly for those who are away from home but are expecting mail.

“Informed Delivery is a secure and convenient tool USPS provides its customers so they know what’s arriving in their mailbox,” said USPS acting Ohio Valley District manager Jean Lovejoy.