There are many different locking mailbox designs on the market now. However, most are variations on the same age old designs the post office has used for decades. There are two basic types of locking mailboxes:
1. There is they kind that has a narrow slot, large enough to fit mail in and some small packages, but not so large that a normal person could not reach their hand inside and access the mail in the locked compartment below.
2. There is the kind that uses a bin, or a tray attached to a door. When you open the door, it lifts the bin. You can put your mail or any packages on the bin and when you close the door, the mail slides down the bin floor into the locked compartment below. When the door is open, the bin is configured such that you cannot reach your hand in and access the contents of the compartment below.
Which one is best? Well it depends on what your needs are. Anything that is depository for packages will be of the type with the bin attached to the door. Most overnight couriers use this type of depository device.
I will cover more about the advantages of the different types in another post.