‘信箱’ (xìn xiāng) literally combines ‘信’ (xìn), meaning ‘letter’ or ‘mail’, and ‘箱’ (xiāng), meaning ‘box’ or ‘container’. Together, it refers to a physical box—usually mounted on a wall, placed outside a home, or located in a building lobby—designed specifically for receiving incoming mail. It is commonly used in residential, office, and institutional settings across China and other Chinese-speaking regions.

Unlike digital mailboxes, 信箱 refers exclusively to physical mail receptacles. It may be public (e.g., street-corner postboxes managed by the postal service) or private (e.g., apartment building mailrooms or individual door-mounted boxes). The word carries no connotation of electronic communication; for email, Chinese uses ‘电子邮箱’ (diànzǐ yóuxiāng). 信箱 is neutral in register and appears frequently in daily life, signage, and postal instructions.