The door front load mailbox manufacturer tells you that in recent years, many mailbox designs with improved structure and security have been patented. With these security designs, the incoming letter is put into a slot or hopper by the mail carrier, where it is put into a secure locked compartment, only for retrieval by the homeowner (they keep the key or lock combination). Door front load mailbox manufacturers tell you that locked mailboxes are usually made of heavy-duty steel or aluminum plates, but some models are made of rotationally molded polymer plastic.

Door front load mailbox manufacturers tell you that due to the increased risk of damage to roadside mailboxes, many vandal-proof boxes made of composite plastic or heavy steel or aluminum plates have also entered the market. Some composite mailboxes made of elastic polymer plastics and mounted on ground nails can withstand severe impacts from baseball bats and can even be crushed by vehicles.
In 1978, the steady increase in the cost of postal services led the USPS to insist on new suburban communities and development of curbside or centralized mail. Door front load mailbox manufacturers tell you that through centralized mail delivery, a central community mail station composed of multiple mailboxes is located in or near a building or in a specific neighborhood. Door front load mailbox manufacturers tell you that these mailboxes are usually called group mailboxes, cluster mailboxes or community mail stations, and are usually used in newer structures instead of door-to-door or roadside mailbox delivery.
Door front load mailbox manufacturers tell you that large apartment buildings usually provide a set of mailboxes for all units, located in the entrance hall or a dedicated mail room nearby. Usually there is a special lock box (also known as "key safe box" or "Knox box") at the external entrance, which can be used by the front door key or directly to activate the front door electric shock, so that the mail can be sent to people entering the building. Door front load mailbox manufacturers tell you that similar "arrow locks" are usually located on centralized mailboxes, so that the entire device can be opened to effectively fill individual mailboxes.