I used to walk by this sign everyday at my former workplace. I never understood it. I'm sure there is a reason why there is an empty mail bin in that spot, but if so many people are throwing their mail in the bin that you need a sign to tell them to stop doing it…isn't the logical thing to just remove the bin?
Also, this seems like an overzealous use of the word WARNING! What exactly would happen if you were dumb enough to drop your mail in this bin? I always wanted to test it. Would you be yelled at? Would a piano drop on your head? Would you be taken to jail? Or would your mail just be stolen?