Our mailbox and its post were falling apart after 20 plus years of faithful service. When we went to the local home improvement store the selection of posts was depressing and expensive so I decided to build my own. The post is two pieces of redwood 4"x4" finished in the Shou Sugi Ban style of burning then brushing the wood. I used a new technique this time to increase the relief and make the spring growth pop a little more. Finish is two coats of tung oil followed by two coats of wipe-on semi-gloss polyurethane.
Instead of having the typical diagonal support on the bottom, I used an L bracket hidden by the mailbox to give it a cleaner look. The posts are glued and fastened with 3" deck screws. I don't think it's going anywhere. I used starboard lumber (like Azek) as the base the mailbox sits on as that will not rust or decay.