Publication 52 - Hazardous, Restricted, and Perishable Mail > 5 Perishable Matter > 52 Animals > 522 Packaging and Markings
Any container used to mail perishable matter must be constructed to protect and securely contain the contents.
Shipping containers for mailable live animals must, at a minimum, be made of 275-pound test, double-wall, corrugated, weather-resistant fiberboard (W5c) or equivalent. USPS-produced packaging, including Flat Rate containers, are not eligible to be used. Additional container requirements apply to mailable adult birds.
Containers must be constructed to prevent escape of animals, prevent the crushing of the container and contents during normal handling, and provide adequate ventilation for the animals at all times.
Each mailpiece must bear a complete return address and be marked on the address side with a description of the contents (e.g., “Live Animals,” “Live Honey Bees,” etc.). A mailpiece marked “If Undeliverable, Abandon” may not be accepted for mailing.