This type of wooden mailbox is along the lines of 'letterboxes' more likely to be found in the City Suburbs of Australasia.
US mailboxes are
designed differently and for the most have postal regulations as to structure and dimensions including height off ground.
In the United Kingdom it still seems to be the
'slot-in-the-door' or the 'slot-in-the-gate' type letterbox that reigns although more recently the standard type rural US mailbox is getting increasingly popular in both
Australasia and the United kingdom.
This particular wooden mailbox can be attached to the side of a post or any other structure.
There is a separate place for letters,
newspapers and parcels or bottles.
Construction material: 18mm (3/4") thick plywood.
Dimensions: 507mm (20 1/4") high, 270mm (10 3/4") wide and 300mm (12") deep.
This project is covered in two pages, firstly the mailbox plans followed by instructions on how to build the mailbox.
Page one: The mailbox plans