USPS Unmailable and Prohibited Items: Bans, Labeling, and Penalties

USPS prohibited and restricted items fall into two groups: a short list of things you cannot mail at all, and a longer list of things you can mail only if you follow specific rules about packaging, service class, and documentation. The outright bans include explosives, ammunition, fireworks, liquid mercury, controlled substances, hazardous waste, poisons, and lottery materials. The restricted group covers firearms, tobacco, lithium batteries, alcohol-based liquids, perishables, live animals, and cremated remains. Getting it wrong is not a paperwork problem: under 18 U.S.C. § 1716, a knowing violation carries up to a year in prison, and mailing hazardous materials in violation of the rules can trigger civil fines from $250 to $100,000 per violation.

What USPS Bans Outright

Some materials are nonmailable no matter how you package them. Explosives head the list. All fireworks, ammunition, primers, and propellant powder are prohibited from both domestic and international mail, air or ground, with no consumer exceptions.¹ Highway and rail distress signals (fusees) are banned as flammable solids. Any device designed to ignite or explode is banned as well.

Liquid mercury is prohibited in any amount, including devices that contain a visible amount of mercury. It is highly toxic and corrodes aluminum, which makes it particularly dangerous aboard aircraft.² Hazardous waste requiring specialized environmental disposal, poisonous materials, and disease organisms are also nonmailable.³

Lottery tickets and related materials are nonmailable regardless of whether the underlying lottery is legal in a particular state. The ban covers any scheme where a prize is awarded by chance and the participant pays to enter, and it extends to checks, money orders, or payments sent to buy tickets or to pay fees for supposed “winnings.”⁴

Marijuana, CBD, and Controlled Substances

Every substance listed under Schedules I through V of the Controlled Substances Act is nonmailable. Marijuana is included. USPS operates under federal law, so state legalization for medical or recreational use does not change the rule: if distributing a substance is illegal under the Controlled Substances Act (21 U.S.C. § 801–971), mailing it is illegal under 18 U.S.C. § 1716.⁵ Drug paraphernalia is banned under the same authority.

The consequences run beyond a mailing violation. Distribution of even moderate quantities through the mail can trigger mandatory minimum sentences under 21 U.S.C. § 841.⁶ The Postal Inspection Service has broad authority to detain, open, and seize suspicious packages, and works with the DEA and other federal agencies.

Hemp-derived products, including CBD, are mailable domestically as long as THC concentration does not exceed 0.3 percent.⁷ That threshold is the federal line between legal hemp and illegal marijuana. International shipments of hemp and CBD are prohibited entirely, and so are shipments to military APO, FPO, and DPO addresses.⁵

Firearms

Handguns, revolvers, and any other firearm concealable on a person are nonmailable to the general public. Federal law limits handgun shipments through USPS to licensed manufacturers, dealers, and importers making customary trade shipments, and to certain military, law enforcement, and government officers acting officially.⁸ A private individual who needs to ship a handgun has to use a private carrier such as FedEx or UPS.

Rifles and shotguns follow different rules. Unloaded long guns are mailable, but the conditions depend on who is sending and receiving:

Shipments between federal firearms licensees (FFLs) are unrestricted, though USPS recommends a service with tracking and signature confirmation.
Individuals may ship rifles or shotguns within the same state if the package carries a “Return Service Requested” endorsement and uses a tracked service with signature capture.
Individuals in any state may mail a rifle or shotgun to a licensed dealer, manufacturer, or importer using a tracked service with signature capture.
You can mail a rifle or shotgun to yourself at an out-of-state address for lawful purposes such as hunting, addressed in care of a temporary custodian, with tracking and signature required.

All firearms shipments must comply with federal (27 CFR Part 478) and state regulations. Licensed dealers, manufacturers, and importers file PS Form 1508 with the postmaster confirming license status and the nature of the shipment.⁹

Tobacco Products

Cigarettes and smokeless tobacco are classified as nonmailable under 18 U.S.C. § 1716E, with narrow exceptions. Businesses can mail tobacco between verified employees under specific rules, and individual adults can mail tobacco for noncommercial purposes, such as returning a damaged product to the manufacturer. In each case USPS must verify that the sender is not a minor, and delivery requires a signature from a verified adult.¹⁰ Manufacturers running consumer testing programs can mail cigarettes to verified adult smokers, but all applicable state and local excise taxes must be paid first. States, localities, and tribal authorities can sue in federal court to recover unpaid taxes on tobacco shipped in violation of these rules.

Lithium Batteries

Lithium batteries are Class 9 hazardous materials. They are mailable, but only within capacity limits. For air transportation, the thresholds are:

Lithium-ion cells: 20 watt-hours or less per cell
Lithium-ion batteries: 100 watt-hours or less per battery
Lithium metal cells: 1 gram of lithium content or less
Lithium metal batteries: 2 grams of lithium content or less

Ground-only transportation allows higher limits: lithium-ion cells up to 60 watt-hours and batteries up to 300 watt-hours, and lithium metal cells up to 5 grams and batteries up to 25 grams.¹¹ Most phones and laptops installed in their equipment fit within these limits, but spare high-capacity batteries for power tools or e-bikes often do not. Cover the terminals with non-conductive tape or seal each battery in an individual plastic bag to prevent short circuits. Standalone lithium-ion batteries ship under UN3480; lithium metal batteries under UN3090.

Alcohol-Based Liquids and Perfumes

Intoxicating liquors (beverages with 0.5 percent alcohol or more by weight) are restricted to authorized shipments. Mailing ethanol-based products by air, including perfumes and colognes, requires prior written authorization from USPS. The sender submits a request to the director of Product Classification with product details, a safety data sheet, and the expected mailing frequency. Initial approval lasts one year.¹²

Even with authorization, strict volume limits apply. Products up to 70 percent ethanol by volume are limited to 16-ounce non-glass containers or 8-ounce glass containers, with a maximum of 96 ounces total liquid per package. Products above 70 percent ethanol are further restricted to 8-ounce containers and 48 ounces total per package. Every approved package must display the authorization number and include a written notice to the recipient warning against re-mailing the contents by air.¹³ Casual senders cannot simply drop a bottle of perfume in the mail. Without the authorization letter, the post office will refuse it.

Perishables, Live Animals, and Cremated Remains

Perishable Food

USPS does not prohibit perishable food, but keeping it safe is entirely your responsibility. Meat, poultry, fish, and other items requiring refrigeration must be sent cold or frozen with a cold source such as frozen gel packs or dry ice. The USDA warns that perishable food held between 40°F and 140°F for more than two hours should not be eaten. A warm package means unsafe food regardless of how it looks or smells.¹⁴

Ship perishables early in the week and use the fastest service available. Dry ice has its own rules: up to 5 pounds per package for air transportation; ground shipments can contain more. Air packages with dry ice must bear a Class 9 hazardous material label, be marked “Carbon Dioxide Solid” or “Dry Ice,” and include a completed shipper’s declaration for dangerous goods. Ground shipments must be marked “Surface Only” and “Dry Ice, UN1845.”¹⁵

Live Animals

Only specific live animals may be mailed, and each type has its own rules:

Honeybees and queen bees, securely packaged with adequate ventilation, kept between 40°F and 100°F, marked “Live Bees” and “Surface Only.”
Day-old poultry (chickens, ducks, geese, turkeys, and several other species), only in the original unopened hatchery box. Pheasants are limited to April through August.
Adult birds, via Priority Mail Express only, between 6 ounces and 25 pounds, in containers designed to minimize light and visual stimuli.
Small cold-blooded animals such as goldfish, tropical fish, frogs, lizards, and nonpoisonous insects. Snakes, turtles, and turtle eggs are specifically excluded.
Live scorpions, only for medical research or antivenin production, in a double-container system where the inner receptacle cannot be punctured.

All mailable animals must be able to survive normal transit times without food or water (fish excepted) and must not create sanitary problems.¹⁶

Cremated Remains

Human and animal cremated remains are mailable only through Priority Mail Express. No other service is permitted. As of March 2025, USPS requires the use of its postal-branded Cremated Remains box (BOX-CRE) for all shipments, including remains incorporated into jewelry, blown glass, or artwork. The inner container must be sift-proof, and USPS recommends placing it in a sealed plastic bag labeled with the sender’s and recipient’s addresses along with the words “Cremated Remains” in case the outer label becomes detached.¹⁷

Packaging, Labeling, and Handoff

The old ORM-D marking was eliminated on January 1, 2021. The only acceptable marking for eligible limited-quantity hazardous materials shipped by ground is now the DOT limited-quantity mark, a plain square-on-point diamond.¹⁸ Packages still bearing the old “Consumer Commodity ORM-D” label will be rejected. Hazardous materials shipments must also display the proper shipping name and UN identification number on the exterior. A wrong or missing UN number can get the package rejected or, if it slips into the mail stream undetected, produce civil penalties later.

Liquids must be sealed in a primary container and then placed inside a leak-proof secondary liner with enough absorbent material to soak up the entire volume if the primary breaks. Corrosive liquids are limited to 16-ounce primary containers.¹⁹ Sharp objects such as knives, razor blades, and ice picks are mailable but must be packaged in a strong container with enough cushioning to prevent the blade or point from cutting through the outer packaging. If you are mailing a switchblade in a jurisdiction where that is legal, the outside of the package must not contain any marking indicating what is inside.²⁰

Restricted materials must be handed directly to a postal clerk at a retail counter. You cannot use collection boxes, lobby drops, package pickup, third-party acceptance locations, Contract Postal Units, or Village Post Offices. Packages placed in those channels can be removed and destroyed.²¹ For tobacco specifically, the sender must orally confirm to the clerk that the addressee is an adult who meets the minimum age requirement at the delivery location. Keep your tracking receipt as proof that you declared the contents and USPS accepted the package. Many restricted materials are limited to ground transportation; those designated for surface shipping must not be placed on aircraft under any circumstances.²²

Penalties for Violations

Penalties run on two tracks. Under 18 U.S.C. § 1716, knowingly mailing any nonmailable item carries up to one year in prison and a fine. If the sender acted with intent to kill or injure someone, or to damage the mail or other property, the penalty rises to up to twenty years. If someone dies as a result, the sentence can be life imprisonment.³

Civil penalties for hazardous materials violations are separate and stack quickly. Under 39 U.S.C. § 3018, a person who knowingly mails hazardous materials in violation of the rules faces fines between $250 and $100,000 per violation, plus cleanup costs and damages. Each noncompliant item counts as a separate violation, and each day the item remains in the mail adds another. USPS sets the amount based on severity, sender history, and impact on postal operations.²³ Controlled substances mailed through USPS trigger a third layer under federal drug laws, which carry mandatory minimum sentences for larger quantities. Even a small personal-use amount of marijuana shipped through the mail is a federal distribution offense, not just a mailing violation.

1
USPS Postal Explorer. USPS Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 341 Explosives
2
United States Postal Service. Shipping Restrictions and HAZMAT – What Can You Send in the Mail?
3
Office of the Law Revision Counsel. 18 USC 1716 – Injurious Articles as Nonmailable
4
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 456 Lottery
5
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 453 Controlled Substances and Drugs
6
Office of the Law Revision Counsel. 21 USC 841 – Prohibited Acts A
7
United States Postal Service. Correction: Publication 52 Revision – Hemp-based Products Update
8
Office of the Law Revision Counsel. 18 USC 1715 – Firearms as Nonmailable; Regulations
9
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 432.24 Certificate of Manufacturers, Dealers, and Importers
10
Office of the Law Revision Counsel. 18 USC 1716E – Tobacco Products as Nonmailable
11
Pipeline and Hazardous Materials Safety Administration. Lithium Battery Guide for Shippers
12
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 343 Flammable and Combustible Liquids
13
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 343.25 Authorization to Mail Ethanol-Based Flammable Liquids
14
Food Safety and Inspection Service. Mail Order Food Safety
15
United States Postal Service. How Do I Keep My Mailed Item Cold or Refrigerated?
16
United States Postal Service. Publication 52 – Hazardous, Restricted, and Perishable Mail – Mailable Live Animals
17
United States Postal Service. Shipping Cremated Remains and Ashes
18
USPS Postal Explorer. DMM Advisory – Reminder: Elimination of the ORM-D Category is Here!
19
USPS Postal Explorer. USPS Packaging Instruction 8A
20
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 443 Packaging and Marking
21
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 473 Mailability Exceptions
22
USPS Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 327 Transportation Requirements
23
Office of the Law Revision Counsel. 39 USC 3018 – Hazardous Material