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Publication 52 - Hazardous, Restricted, and Perishable Mail >
2 General Guidelines > 21 Mailability > 216 Nonmailable Matter Found in the Mail
Specific items, such as firearms, switchblade knives, controlled substances, motor vehicle master keys, and explosive or incendiary devices, generally are prohibited for mailing. When these types of nonmailable items are found in the mailstream, they must be handled in accordance with POM 139.117, by referring to the Postal Inspection Service.
Other materials found in the mail that are believed to be nonmailable must be treated under the applicable conditions in POM 139.117-18 and ASM 223.4.