What the Postal Service won't send abroad — and why USPS is stricter than the express carriers
USPS uses the term "non-mailable matter." Domestic rules live in USPS Publication 52; international rules add the destination country's Individual Country Listing in the International Mail Manual (IMM). Because USPS moves most international mail by air and cannot offer a dangerous-goods declaration the way FedEx, UPS, and DHL can, it bans many things the express carriers will still carry under contract — most fragrances, most alcohol, and loose batteries among them. Check the official IMM prohibitions and your country's listing before mailing.
Allowed internationally only when installed in the device they power, within quantity limits — never as loose spares.
Generally only mailable by licensed entities; personal medication is restricted and often blocked by the destination.
Permitted if non-hazardous, sealed, leak-proof, and within the destination's limits; many countries cap or ban them.
Non-perishable, commercially sealed food is often allowed; perishable, meat, and dairy are widely banned.
Ordinary tools usually fine; automatic/concealed knives are non-mailable.
Permitted but uninsurable above low limits; registered mail recommended.
Even when USPS would accept an item, the destination's Individual Country Listing in the IMM can prohibit it. The listing for each country names the specific goods that nation bans from inbound mail — used clothing, certain electronics, religious or political material, and more. Pair the country listing with our destination guides and the universal prohibited items list for the full picture.