Hi Vee, following on your idea, keep letter box key in car boot. Have PO Box for security of mail ever since '92, when mail stolen, which included ticket to 'Phantom', in Melbourne! That inconvenience was a right pain in the ....!
I do not lock my letterbox,and have never done so or thought of doing so! Maybe I am just the least paranoid person on the planet!!! If anyone would like my identity,they are welcome to it as long as they also take the illness I suffer with every day! Ha ha ha ha ha!!!!
I'm surprised to see others don't lock their mail boxes.
My son is a Locksmith & is forever putting lock's on mail boxes, at units...that have broken ones.
After talking with a fair few who have had Identity theft, he tells me they say their lives have been turned up-side-down!! And became a living nightmare, and they had to prove who they were.It turns out to be a dreadful problem to fix!