Letters and postcards should be what shape?

Letters and postcards are required to be rectangular in shape to ensure proper handling and processing within the postal system. The rectangular dimensions conform to the standard sizes used for mail, which facilitates efficient sorting and delivery. This shape allows machines and postal workers to easily manage and organize the mail, reducing the risk of misdelivery or delays.

Rectangular mail pieces also fit neatly into sorting equipment and envelopes, maximizing space and optimizing the transportation and delivery processes. Options like square, triangular, or round shapes do not align with the standard practices of postal services, which typically utilize rectangular formats to enhance efficiency and reduce operational costs. Thus, rectangular shapes are fundamental for maintaining the integrity and functionality of postal operations.