the post is metal and the flat part that the mailbox will sit on, has holes in it. I have a new mailbox that is standard and needs to be attached to a piece of wood. I see now that the current lousy mailbox is being held on by some kind of metal wire run in between the mailbox and the wood and then tied around the post - not sturdy.
If your standard box is like the ones we country folks have, using the holes in the metal, attach a 1- x - xx - x - xx piece of wood to the metal plate. The recess on the under side of the box will determine the xx dimensions. The lower sides of the box are then screwed to the 1x edge with non rusting screws.