h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Letterboxes? Looxury! I live in a small Danish village where such things are few and far between. I discovered this when I had to distribute a note warning that the water would be cut off briefly the next evening (I'm the unpaid treasurer of our village water company, with 36 customers).
It was dark, and there are only a few lampposts. People go to bed early, but the dogs sleep lightly, so I had to beat the retreat some places (actually, some of the owners are scarier than their dogs). So some letterboxes I found the next morning. But for 1/3 of the houses, there is no letterbox - not in the front door, or a mailbox anywhere. And for almost all houses, there is no doorbell.
The owners say the postman knows to go into the house and put the letters on the table. If on rare occasions they are away for so long that they lock the door, the postman knows to put the letters in the milking room (we're talking farmers here).
Some had 'mailboxes' that were visible even at night, but were not recognisable to the uninitiated eg. an old milk churn on the lawn near the road. Others have standard ones fixed to the fence, but never look in them unless they weren't at home when the postman called.
There's some pretty knowledgable postmen round here!