The US Postal Service is testing a “notification” service that emails customers images of the envelopes of their letter-size mail.

The service, called Informed Delivery, will send out an email to customers each morning with that day’s mailbox contents. The images are only of the exterior front side, and the mail will not be opened.

Informed Delivery has been live in seven Northern Virginia zip codes since 2014 and is now expanding to the New York City metro area, with more coverage planned in 2016. The service is free, but customers have to sign up online. It is not available to businesses and will not apply to packages, though the agency said it may include scans of catalogs and magazines in the future.

In 2013, the postal service acknowledged that it photographs every letter and package mailed in the US. The process helps it sort mail, according to the postmaster general. But the USPS has also provided the photos to law-enforcement agencies in criminal cases, including ricin-laced letters sent to US president Barack Obama and Michael Bloomberg, then mayor of New York City. Its mail-tracking program was created after the anthrax attacks in 2001, which killed five people, including two postal workers.