I see what you were doing here. You had a bunch of barely useful crap that you didn't want anymore, and your conscience wouldn't allow you to pitch it directly into landfill. So you drove around the block for roughly three minutes looking for a Vinnie's bin and found a mailbox instead, promptly concluding that parking your crap beside any large metal box with a handle is obviously an ethically and logically superior course of action to just chucking it in your bin.
What amazes me is that this bunch of barely useful crap was actually gone the very next day, while similar piles of crap all over Rezza have lain in situ on kerbsides for months. Maybe this person is onto something.