How do you mail a letter? The easiest way, where I come from, was to either have the stamped addressed letter sticking out of the mail slot in your front door or to put it in your mail box and put the flag up. In either case, the mail carrier would pick it up. 

So naturally, when we moved to the Netherlands, I did this. 

The mail carrier kept pushing it back in the front door with the rest of the mail. 

I kept putting it back in the front door mail slot.

After several days of mutual frustration, I asked a friendly Dutch person how to mail a letter. It was quite simple. Bring it to the post office or drop it in one of these orange Dutch mail boxes. Easy, once you know the system. Baffling and frustrating if you do not.

I, the stranger, am deeply grateful for the locals who were (and are) willing to help me cope in this strange land. Consider being a helpful local when you see a stranger in your own land.  

Matthew 25:35 " . . . I was a stranger, and you welcomed me . . ."