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What Materials Can Curbside Mailboxes Be Made Of?

Thursday July 30, 2020

If you're shopping for new curbside mailboxes, you might be wondering what materials are allowed. The United States Postal Service (USPS) requires manufacturers to follow specific guidelines when designing curbside mailboxes. Unless a curbside mailbox is made of an appropriate material, it will be rejected. Rejected mailboxes, of course, can't be used for mail delivery purposes. So,w hat materials can curbside mailboxes be made of?


Many curbside mailboxes are made of plastic. It's an inexpensive material that offers strong protection against moisture and the elements. The downside to plastic curbside mailboxes is that they are somewhat weak when compared to those made of other materials. Plastic often deforms or breaks when exposed to stress.


While not as common as plastic, some curbside mailboxes are made of wood. The USPS doesn't prohibit manufacturers from using wood in the construction of their curbside mailboxes. Wood is allowed as long as it's treated to protect against rot and decay. With that said, neither the door handle nor the carrier signal flag can be made of wood. Only the mailbox itself can be made of wood. According to the USPS, plastic is the preferred material for door handles and carrier signal flags.

Ferrous Metal

The USPS also allows curbside mailboxes to be made of ferrous metal. Ferrous metal consists of iron-based metals, such as pure iron, steel, carbon steel. They are recognized for their superior strength and durability. With iron, though, ferrous metal is susceptible to rust. It may rust when exposed to moisture, such as humidity or rainfall. Therefore, manufacturers must treat their curbside mailboxes with a protective finish if they use ferrous metal to make them.

Nonferrous Metal

Along with ferrous metal, nonferrous metal can be used in the construction of curbside mailboxes. Ferrous metal, on the other hand, consists of any type of metal that doesn't contain any noticeable amount of iron. Examples include aluminum, titanium, zinc, brass and copper. Rust only occurs in iron-based metals. As a result, curbside mailboxes made of nonferrous metal are generally protected against this phenomenon. They can still corrode, but they can't rust. And corrosion can be prevented with the use of a protective finish.

As you can see, the USPS doesn't require curbside mailboxes to be made of any single and specific material. They allow manufacturers to design their curbside mailboxes in plastic, wood, ferrous metal or nonferrous metal. The only exception is that carrier signal flags and door handles can't be made of wood; they must use an alternative wood, preferably plastic.


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