USPS Mail Prohibitions, Restrictions, and Penalties

Federal law bars a specific list of items from the U.S. mail entirely and forces many others into narrow packaging, labeling, and mail-class rules. The short list of what you can’t mail through USPS covers explosives and ammunition, illegal drugs and paraphernalia, poisons and disease agents, bulk liquid mercury, cigarettes and smokeless tobacco, alcoholic beverages, vaping products, concealable firearms sent by private individuals, and anything oversized, leaking, or too fragile to survive automated sorting. The governing authorities are USPS Publication 52 and 18 U.S.C. § 1716, which makes it a federal crime to mail anything that could kill or injure a person or damage other mail.1Office of the Law Revision Counsel. 18 USC 1716 – Injurious Articles as Nonmailable

Items Banned Outright

Some things are nonmailable no matter how carefully you pack them. Under 18 U.S.C. § 1716, anything that can explode, ignite, poison, or injure people or damage postal equipment is prohibited.1Office of the Law Revision Counsel. 18 USC 1716 – Injurious Articles as Nonmailable The main categories:

Firearms

USPS treats handguns and long guns very differently. Pistols, revolvers, and any firearm that can be concealed on the person, including short-barreled rifles and shotguns, are nonmailable for most senders.4Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 431 Definitions Only licensed manufacturers, licensed dealers, and certain law enforcement personnel may mail handguns, and they must file an affidavit with the post office first.5Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 432 Mailability

Private individuals can mail unloaded rifles and shotguns, but the shipment must use a mail class that includes tracking and a signature at delivery.5Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 432 Mailability A rifle needs a barrel of at least 16 inches and a shotgun at least 18 inches. Anything shorter is classified as a handgun regardless of appearance.

Tobacco, Alcohol, and Vaping Products

Cigarettes and smokeless tobacco are nonmailable under 18 U.S.C. § 1716E. USPS cannot accept any package it knows or has reason to believe contains these products.6Office of the Law Revision Counsel. 18 USC 1716E – Tobacco Products as Nonmailable Narrow exceptions cover cigars, mail sent within Alaska or Hawaii, shipments between licensed businesses for manufacturing or regulatory purposes, and small noncommercial mailings by adults, such as returning a defective product to a manufacturer. A violation can bring up to one year in prison plus a civil penalty of ten times the retail value of the tobacco, including all federal, state, and local taxes.

Alcoholic beverages follow a similar pattern. Consumers cannot mail beer, wine, or spirits through USPS. The exceptions are narrow, covering products that contain alcohol but are not classified as taxable beverages, like cooking wine, and shipments between government agency employees for official testing.7Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 42 Intoxicating Liquors

Vaping products were added to the prohibited list in 2021 when Congress amended the Prevent All Cigarette Trafficking (PACT) Act. USPS is now barred from shipping electronic nicotine delivery systems, which covers e-cigarettes, vape pens, pods, refill liquids, and any component or accessory.8Bureau of Alcohol, Tobacco, Firearms and Explosives. Vapes and E-Cigarettes

Cannabis, Hemp, and CBD

Marijuana is nonmailable everywhere in the USPS system, state legalization notwithstanding. Hemp-derived products, including CBD, are mailable domestically, but only when THC concentration stays at or below 0.3 percent. The mailer must comply with all federal, state, and local laws on hemp production and sales, and must keep records proving compliance (lab test results, licenses, or compliance reports) for at least three years after mailing.9Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 453.37 Hemp-Based Products Hemp and CBD cannot be sent internationally or to military addresses (APO/FPO/DPO).10USPS. Shipping Restrictions and HAZMAT

Items You Can Mail, But Only With Special Rules

A separate category of items is often mistakenly assumed to be banned. These ship legally when you follow specific packaging, labeling, and mail-class requirements.

Lithium Batteries

Rechargeable lithium-ion batteries in phones, laptops, and cameras are mailable when each cell stays at or below 20 watt-hours and each battery at or below 100 watt-hours.11Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 349 Class 9 Hazardous Materials For air transportation, the batteries must be installed in or packed with the device they power. You cannot send a loose lithium-ion battery by air through USPS. Surface shipping allows standalone batteries in their original sealed packaging. Every shipment needs individual cushioning, separation between batteries, and a DOT Limited Quantity mark on the outer box.

Perfume and Alcohol-Based Fragrances

Perfume is a flammable liquid. It can ship domestically only via surface transportation (USPS Ground Advantage), not Priority Mail or Priority Mail Express. The total volume in a single package cannot exceed 16 ounces. Each container needs absorbent cushioning and a sealed secondary layer such as a zip-lock bag, all inside a strong outer box marked with the DOT Limited Quantity surface designation.12USPS. What Does USPS Classify as Hazardous Materials International perfume shipments are prohibited.

Devices With Small Amounts of Mercury

While bulk liquid mercury is banned, manufactured items like compact fluorescent bulbs that hold tiny amounts of mercury can ship domestically. Each device is limited to 100 milligrams of mercury and each package to 1 gram total. The device must be sealed, cushioned with noncombustible absorbent material, and placed in strong outer packaging labeled “Manufactured Devices Containing Less Than 100 mg Mercury.”3Postal Explorer. Publication 52 – USPS Packaging Instruction 8C International shipments of any item containing mercury are prohibited.

Dry Ice

Dry ice is common for keeping food and medical specimens cold. The air limit is 5 pounds per mailpiece.13Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 743 Perishable Matter with Dry Ice Surface shipping has no stated per-piece weight cap. In both cases the container must be leak-proof but not airtight, since venting carbon dioxide gas prevents pressure buildup that could rupture the package.14USPS. How Do I Keep My Mailed Item Cold or Refrigerated Dry ice is prohibited in all international mail.

Live Animals

USPS accepts a narrower list of live animals than most senders expect. Mailable animals include honeybees, day-old poultry, adult birds in pre-approved containers, live scorpions in limited circumstances, and small harmless cold-blooded animals like lizards, frogs, and salamanders. Snakes, turtles, and turtle eggs are not mailable.15Postal Explorer. Publication 52 – Hazardous, Restricted, and Perishable Mail – Section 526 Mailable Live Animals Packaging rules are strict. Bee shipments by air are limited to one queen and eight attendant bees per mailpiece with a temperature range of 40°F to 100°F. Day-old poultry must go in the original, unopened hatchery box with the hatching date and time on the outside. Adult birds need containers that have passed a three-day survival test including exposure to temperatures between 0°F and 99°F.

Plants Crossing State Lines

Perishable plants and food are mailable when packaged to prevent leakage and odor. Senders shipping plants interstate face an added layer of federal quarantine rules enforced by the USDA’s Animal and Plant Health Inspection Service. Under 7 CFR Part 301, moving regulated plants, soil, or related materials out of a quarantined area generally requires a certificate that the item is pest-free or a limited permit for movement to a specific destination for treatment.16eCFR. 7 CFR Part 301 – Domestic Quarantine Notices Federal quarantines cover dozens of pests, from citrus greening to the Asian longhorned beetle. Check whether your origin or destination sits inside a USDA quarantine zone before shipping.

Cash

You can mail cash, but standard mail services cap insurance for lost or damaged currency at $15. Registered Mail raises that ceiling to $50,000.17USPS. What are the Limits for Insuring Cash and Checks You can declare a higher value, but USPS will only pay out up to $50,000. For anything above that, a wire transfer or armored courier is the practical route.

Size and Weight Limits

Even with nothing hazardous inside, USPS will refuse a package that exceeds 70 pounds or 130 inches in combined length and girth (length plus the distance around the thickest part).18USPS. Parcel Size, Weight, and Fee Standards Packages that fit those bounds but have awkward shapes, like very thin envelopes, long tubes, or flexible polybags, can still jam sorting equipment. Liquids require double-sealed containers with enough absorbent padding to soak up the full volume if the inner container breaks.19Postal Explorer. Publication 52 – USPS Packaging Instruction 3A If a package is too fragile for normal handling, the post office can reject it.

International Mail Prohibits More

Everything banned domestically is banned internationally, and the list grows. Items that are merely restricted for domestic surface shipping, such as perfume, aerosols, dry ice, nail polish, and hemp products, cannot enter international mail at all.20USPS. International Shipping Restrictions Each destination country then adds its own list. Before shipping abroad, check the USPS Individual Country Listings for the destination. Mail to APO/FPO/DPO addresses is priced as domestic but must still comply with the host country’s laws.

Penalties for Mailing the Wrong Thing

Penalties climb sharply with intent. Knowingly mailing something declared nonmailable under 18 U.S.C. § 1716 carries up to one year in prison and a fine. If the sender intended to kill or injure someone, the maximum rises to 20 years. If someone dies, the penalty can be life imprisonment or death.1Office of the Law Revision Counsel. 18 USC 1716 – Injurious Articles as Nonmailable

On the civil side, mailing hazardous materials in violation of 39 U.S.C. § 3018 triggers a penalty of $250 to $100,000 per violation, plus cleanup costs and damages. Each day a noncompliant item sits in the mail system counts as a separate violation, so totals escalate quickly.21GovInfo. 39 USC 3018 – Hazardous Material You don’t have to know the specific rule you broke. Acting without reasonable care is enough for liability.

If the Postal Inspection Service seizes a package, the sender gets written notice within 60 days of the seizure. That notice identifies the property, the legal basis for the seizure, and the claim deadline, which must be at least 35 days from when the notice is sent.22Federal Register. Inspection Service Authority – Seizure and Forfeiture Miss that window and the government can proceed with administrative forfeiture without a hearing.