A mail depository is a secure location where mail is stored and processed. It is typically used by businesses, government agencies, and other organizations to store and manage large volumes of mail. The term 'DROP' is often used to refer to the act of depositing mail into a mail depository. This process involves placing the mail into a designated receptacle or container, which is then securely locked and monitored. Mail deposited in a mail depository is usually sorted and processed before being sent out for delivery.