The U.S. Postal Inspection Service’s mission is to protect the United State Postal Service, its employees, and its customers from criminal attack, as well as protect the Nation’s mail system from criminal misuse. Through a cooperative effort, postal inspectors work with Federal agents, police officers, sheriffs, and other local and State officers and prosecutors when investigating certain postal crimes. In order to continue this successful cooperative approach, the U.S. Postal Inspection Service designed this guide to assist Federal, State, and local law enforcement agencies in understanding how the Postal Inspection Service can assist in investigations. It provides information on postal crimes for which a Postal Inspector should be notified or contacted. Within the guide numerous issues are discussed in brief and include: (1) the Postal Inspection Service’s investigative authority; (2) how postal inspectors and law enforcement agencies can continue to assist each other; (3) crime prevention materials; (4) jurisdiction and laws; (5) Federal laws for selected postal and postal-related crimes; (6) mailbox vandalism; (7) mail fraud; (8) identity theft; (9) narcotics in the mail; (10) child pornography in the mail; (11) asset forfeiture; (12) money laundering; (13) post office box and change of address information; (14) search warrants for mail; and (15) arrest of on-duty postal service employees.