laststandonzombieisland

In 2013, the USPS Postal Inspection Service made some 49,000 mail covers. A mail cover is an investigative tool used to record data appearing on the outside of a mailpiece. Law enforcement agencies use this information to protect national security; locate fugitives; obtain evidence; or help identify property, proceeds, or assets forfeitable under criminal law.

In short, if you are under investigation, the USPS may be making a photocopy of the outside of your mail. True story.