A letter that is square instead of rectangular is classified as what type of mail?

A letter that is square rather than rectangular is classified as non-machinable because it does not conform to the standard dimensions and characteristics required for machinable mail. The USPS has specific guidelines for mail shapes and sizes, and machinable mail must meet certain criteria allowing automated sorting and processing. Square letters typically require manual handling, increasing their processing costs and delivery time, which is why they are categorized separately.

In the context of postal services, machinable mail refers to those items that can be processed automatically through sorting machines, while non-machinable items necessitate manual processing due to their shape, size, or other factors. This classification affects postage rates and handling procedures. Thus, identifying square letters as non-machinable is accurate and aligns with USPS regulations regarding mail processing and handling.