This is probably a reference to US postal or mail covers. The USPS takes images of most or all postal mail as part of its delivery and postal sorting/routing p

This is probably a reference to US postal or mail covers. The USPS takes images of most or all postal mail as part of its delivery and postal sorting/routing processes. Those covers are retained for a limited period of time, and actually have, so far as I understand, significant privacy protections associated with them, of the sort notably absent in most electronic communications. See: Mail Cover (Wikipedia): Mail cover is a law enforcement investigative technique in which the United States Postal Service, acting at the request of a law enforcement agency, records information from the outside of letters and parcels before they are delivered and then sends the information to the agency that requested it.[1] The Postal Service grants mail cover surveillance requests for about 30 days and may extend them for up to 120 days. <https://en.wikipedia.org/wiki/Mail_cover https://en.wikipedia.org/wiki/Mail_cover> MICT: Mail Isolation Control and Tracking (Wikipedia): [A]n imaging system employed by the United States Postal Service (USPS) that takes photographs of the exterior of every piece of mail that is processed in the United States.[1] The Postmaster General has stated that the system is primarily used for mail sorting,[2] though it also enables the USPS to retroactively track mail correspondence at the request of law enforcement.[2] It was created in the aftermath of the 2001 anthrax attacks that killed five people.. <https://en.wikipedia.org/wiki/Mail_Isolation_Control_and_Tracking https://en.wikipedia.org/wiki/Mail_Isolation_Control_and_Tra...> 39 CFR § 233.3 - Mail covers. <https://www.law.cornell.edu/cfr/text/39/233.3 https://www.law.cornell.edu/cfr/text/39/233.3>