Mailboxes are situated on the curb away from the house where they are easily accessed by mail delivery workers. Every day each postal delivery worker delivers hundreds of pieces of mail. It is not unreasonable to expect that there are strict federal requirements for mailboxes to which customers want their mail delivered.
An example of identification requirements is that the address number should be clearly displayed on the outside of the box. Such identification numbers need to be of a certain height, at least 1 inch it turns out, so that they are visible to a mail worker who is looking from the road.
Lettering that satisfies the minimum size but is of a color that blends into the background so much that is becomes invisible is also useless. Therefore, it is required that the coloring be contrasting with the background. Otherwise the U.S. Postal Service is not responsible for undelivered mail.
In cases where the house is built in a place that it is impossible to put a mailbox on the street, one can always put it on an alternate street. This happens when there is no curb or space. Separated boxes are fine as long as they are labeled properly, ideally also with the name of the mail recipient.
It is perhaps a bit surprising to know while the design, style, color and font of the numbering is entirely up to the individual taste, no advertising of any sort is allowed on the mailbox. This goes for both for-profit and non-profit advertising purposes.
While simply painting your mailbox with numbers might appear like an easy form of address sign, it demands repainting at normal intervals as the paint can fade because of rain and snow. A little of elegance is introduced by having your address on a weather-resistant metal plaque attached to the top of your mailbox and offers you one less chore to perform.