The word "邮箱" is formed by combining two meaningful characters: "邮" (yóu), which conveys the core idea of "mail" or "postal matters", and "箱" (xiāng), which means "box" or "chest". Together, they create a direct, compound concept of a "mailbox", a literal box for mail. This conceptual pairing visually and functionally defines the object, and by modern extension, it naturally adopts the meaning of an "email inbox", preserving the essential idea of a receptacle for messages.