And if you receive an item in your letterbox that has been posted to your address by mistake (ie, it is has a different address to your address), simply pop it into a red street posting box.
Whatever you do, don’t open it.
Tampering with mail is considered a serious offence in Australia, and throughout the world, and the penalty is harsh: a maximum of five years' imprisonment in Australia.
There are various reasons why people might open someone else’s mail, ranging from curiosity (opening a payslip of a previous tenant) to treachery (examining an ex’s bank statement after he/she has moved out). People have also been known to open their partner's mail in the hunt for hidden wealth.
But what if you do it accidentally?
Let’s say you receive someone else’s mail in your letterbox, and because it looks like something you might get (an insurance renewal, for example) you accidentally open it. Thankfully, this is not an offence.
In other countries, the law is pretty much the same, the difference is in the penalties. In the US, if you deliberately open someone else's mail the maximum penalty is set at three years, while in Germany it’s one year.
Still, that's a lot of time for opening an envelope not addressed to you. So mind your own business - and as the song goes, return to sender.