I built an oak mailbox for my townhouse when I was a teenager, and I finished it the same way I finished the interior furniture I was making at the time: clear satin polyurethane. The mailbox looked good enough that strangers driving by noticed it, came to the door and asked if I would build one for them too. Unfortunately, my experience with exterior wood finishes was found with both mailboxes. Within a year, the hand-rubbed finish had wilted and failed miserably. Now I know better, but the secrets to a durable exterior finish aren’t always clear.
