What you can not ship

Every label is bound by the carrier's own rules. Do not ship:

• Explosives, fireworks, ammunition, flammable liquids or gases, and other hazardous materials unless the carrier's own hazardous service is used
• Illegal drugs, marijuana and items that break federal or state law
• Live animals, except where the carrier allows them
• Cash, gift cards in bulk, or other items the carrier does not accept
• Lithium batteries outside the carrier's packing rules

See the full lists from USPS Publication 52, UPS and FedEx.