Here is a Gibraltar Gentry (Rubbermaid) mailbox and post assembly we installed in Lisle, Illinois. These mailboxes mount over a wood post that is set 2′ into the ground with cement. The customer supplied the mailbox (typical cost $50-$65) and come in black or mocha (as shown) color. We professionally installed it including the wood post and cement for $175.
For kicks, here is what the customer was using for her mailbox prior to our installation: