The United States Postal Service is responsible for getting packages to their destinations as efficiently as possible. Its priority mail service gets most packages to their destinations between one and three business days. However, even the USPS has its limits, so it places restrictions on what you can ship domestically and internationally.
Prohibited Domestic Items
If you’re using flat rate shipping for shipments inside the U.S., anything you mail must fit into the box or envelope so that it closes within the normal folds. You can’t ship air bags, ammunition, explosives or gasoline to any domestic or international destination. Nor can you ship cigarettes or smokeless tobacco. With few restrictions, pets and warm-blooded animals can’t be mailed. Even nail polish and perfume have restrictions. Depending on their ingredients, both may have to be shipped by ground because of their toxicity or risk of catching fire.
Check with the USPS if you have questions about international restrictions, as they can vary between products and destinations. Tobacco restrictions vary by country, so cigars may be mailed to some locations but not others. Certain products that can be mailed domestically, like small lithium batteries, medical devices or safety matches, can’t be sent internationally in most circumstances.
Some items can only be mailed if packaged in a designated way or for a specific purpose. You might be able to mail aerosols, dry ice, glues, live animals, paint and cremated remains, but only if you follow strict guidelines. Check with the post office to confirm you’re meeting the requirements for doing so. Prescription drugs can only be mailed by distributors recognized by the Drug Enforcement Administration. Only licensed firearm dealers can mail or receive handguns.