There are some items you can’t ship with USPS—no exceptions!
Reference the USPS Postal Explorer before buying any labels
Before labels for any package that contains dangerous, hazardous, or restricted items, we suggest checking the USPS Postal Explorer to follow along with any packaging instructions.
Packaging instructions: Be sure to read all the USPS rules and packing instructions in Publication 52 of the Postal Explorer if you want to ship any package that contains dangerous, hazardous, or restricted items.
Following the rules and instructions provided by USPS is your responsibility as the shipper.
You’ll notice that all prohibited domestic items are also prohibited from being shipped internationally. However, some items are only prohibited internationally and not domestically (such as aerosols and dry ice).
Prohibited domestic items
Airbags
Alcoholic Beverages
Ammunition
Explosives
Gasoline
Marijuana, including marijuana intended for medicinal use
An exception is marijuana seeds or hemp-derived CBD products with less than 0.3% THC content and with no intent to grow
Mercury (according to USPS, this includes devices containing metallic mercury such as antique thermometers, blood pressure monitors, barometers, and other similar products)
See the Postal Service's FAQ on prohibited items containing mercury
Prohibited international items
Aerosols
Airbags
Alcoholic Beverages
Ammunition
Cigarettes (these include electronic cigarettes, e-cigars, vaping products, and any components associated with these devices)
Dry Ice
Explosives
Flammable Liquid
Fresh Fruits and Vegetables
Gasoline
Lighters
Marijuana, including seeds, and marijuana intended for medicinal use
Nail Polish
Perfumes (containing alcohol)
Poison
Disclaimer for sending hazardous or dangerous goods
As we said at the top of this article, any package containing dangerous, hazardous, or restricted goods must comply with all applicable rules and regulations in USPS Publication 52 - Hazardous, Restricted, and Perishable Mail.'