"As one of our country's oldest federal law enforcement agencies, founded by Benjamin Franklin, the United States Postal Inspection Service has a long, proud, and successful history of fighting criminals who attack our nation's postal system and misuse it to defraud, endanger, or otherwise threaten the American public. As the primary law enforcement arm of the United States Postal Service, the U.S. Postal Inspection Service is a highly specialized, professional organization performing investigative and security functions essential to a stable and sound postal system. Congress empowered the Postal Service 'to investigate postal offenses and civil matters relating to the Postal Service.' Through its security and enforcement functions, the Postal Inspection Service provides assurance to American businesses for the safe exchange of funds and securities through the U.S. Mail; to postal customers of the 'sanctity of the seal' in transmitting correspondence and messages; and to postal employees of a safe work environment."
United States Postal Inspection Service: https://postalinspectors.uspis.gov/