Abstract: An improved mailbox is provided which includes a security subassembly. The security subassembly includes an elongated sleeve which is fixed into position relative to a mailbox. It further includes a security door which is locked into position relative to the elongated sleeve. A mail slot is provided in the security door which allows for a mail carrier to deposit mail within the central cavity of the mailbox. A locking mechanism is provided to allow the security door to be moved between a normally closed condition and an open condition to allow the authorized user to remove mail from the central cavity of the mailbox.