We have a locked mail box on a post by the entrance to our drive.
Our postman comes down the chemin rural does a sweep into our drive turning the van so it's alongside the box and leans across and puts the post in without getting out. When he has a large package (usually something from Amazon) which won't go through the slot, he has a master key to unlock the box. He grumbles from time to time about having to drive down the chemin and says we should put the box right at the top on the road. That would mean we would never see him, which would be a shame. He doesn't grumble much - I think he likes his Christmas Box - so we've left the postbox where it is.
We only have the one key. And we've been saying for over two years that we must get a copy. It comes on a fluffy small teddy bear key ring with a not too robust clip. Unwise to have something small and fluffy lying around with an Airedale terrier in the house.
Yesterday I dropped the key and didn't notice. Vita did, grabbed it and then proceeded to "kill" the small teddy bear all round the garden. By the time I rescued the key ring there was no key.
The advice from someone on Total France: "Go to your local brico and buy a new barrel (barillet) that is PTT agreed. Ask the postman to open your box and leave it open. Change the barrel."
So the post box now has a note attached to it (hope my French makes sense).
I'll make sure the new barrel has at least two keys and I'll get two very non-furry key rings.