What is mailbox in door?

A mailbox in a door is a mailbox that is installed directly into the front door of a residential or commercial building. It typically consists of a small rectangular or circular opening on the exterior of the door, which allows mail to be inserted into the mailbox from the outside. On the inside of the door, there is a secure compartment where the mail is collected and stored until it is retrieved by the homeowner or tenants. Some mailbox doors also have a locking mechanism, which enhances security and prevents unauthorized access to the mail. This type of mailbox is convenient for those who do not have a dedicated mailbox outside their home or office and provides a discreet and secure way to receive mail without having to go outside to a mailbox.