One Sunday when my family was out of town, my neighbor Joe and I spent roughly 10 hours building and installing this mailbox. The next day, I got a notice from the mailman saying that it didn't meet official mailbox standards, and that it would have to be fixed. It wasn't the right height and the hinge had to be on the bottom, not on the top.
I wasn't about to remove it, because I was quite proud of my creation, and the whole thing weighs over 500 pounds. So I talked with the mailman and found out that her real objection was that it took two hands to deliver the mail: one to hold the lid up, and one to insert the mail. So I went to Reid Tool Supply and ordered solid stainless steel "spring plungers", which I mounted using stainless steel nuts welded to the inside of the lid (see below).
The mailman now delivers the mail with one hand, and I didn't have to rent a crane to remove the box. :)