Remember that Elvis Presley song 'Return to Sender'? He sings about being a young man in love who is trying to apologize, via letter, to his girlfriend but the postman keeps bringing the letters back. The envelope is always marked "Return to Sender, Address Unknown, No Such Person, No Such Zone". When Mr. Presley was singing this song the postal service was much different than it is today. Everything was delivered via the post, hazardous or not. There was still Saturday delivery, and when you mailed a letter to someone in the same city, they got it the next day. Nowadays we are lucky if it gets to its intended recipient within a week. Plus, with the advent of electronic mail the postman's bag is filled more with bills and flyers than love letters. Let's look at some of the items the United States Postal Service (USPS) has banned from their delivery service. You may be surprised by the inclusions of seemingly innocent household substances.

The general rule with the USPS is that if the material can cause harm to anyone or anything, then it is a hazardous material. Keep in mind that during transit, postal items may encounter extreme temperature changes, significant vibration and fluctuations in atmospheric pressure. Examples of restricted items many people have in their homes include: perfumes, nail polish, anything aerosol, flea collars or sprays, matches, batteries and mercury thermometers. If any of these materials become too warm under pressure, such as in the cargo hold of an airplane, they will explode. Less common, but just as volatile, substances restricted by the USPS include: pool chemicals, household paint, any kind of fuel, any container that previously held fuel, airbags, dry ice, glue, fireworks and cleaning supplies. Alcoholic beverages are not deemed hazardous by the USPS, but are on the list of prohibited items. Additionally, boxes displaying markings indicating alcohol are also not allowed.

The above lists of hazardous items refer to postal services within the US, but what about items sent from outside the US? If you know a friend or relative is going to send gifts for Christmas or a wedding, then it is probably a good idea to make sure they are aware of import restrictions. For example, over the last ten years there has been resurgence in popularity of Absinthe, an alcoholic beverage with supposed hallucinogenic properties. During the mid-19th century, Absinthe was very popular all over Europe and North America, but after the Temperance Movement the beverage was demonized by claims that those who consumed it were responsible for violent crimes and social disorder. The 21st century outcome is that Absinthe cannot be shipped or imported into the US if: it contains more than 100 parts per million of thujone, the brand name is Absinthe, the word "absinthe" stands alone on the label or the graphics display mind-altering effects or drinking the beverage. So if you have an uncle in France, tell him not to send Absinthe.

Logic will guide most people in determining what should and should not be sent via post. Within the US, the rules are basically centered on safety. Don't ship anything that could explode or harm anyone if the package leaked. Shipping to the US from outside the country is a bit more of a complicated situation. Protecting the flora and fauna from foreign predators is important in order to prevent crop depletion. For example, bringing fruit or vegetables home from a trip to the Mediterranean may seem innocent, but consider the fruit fly infestation the took place in the 1980's. A single traveler brought one piece of infested fruit home to California after a vacation abroad and the subsequent infestation cost the US government an estimated $100 million dollars to remedy. The same lesson applies to sending food items home from abroad. Bugs can just as easily hop a ride to the US in a package as they can in your luggage. Before choosing your gifts to send to friends and relatives, think carefully about postal restrictions.