I wanted to share the method (works wonderfully) I used to install a motion sensor in my mailbox. There are a total of 4 pictures with captions.
I’ll bet postal workers find all sorts of upgrades these days, and probably ignore modifications to federal property.
They are considered Federal property once installed for mail pickup and delivery. Up until that point they are either property of the mfgr, reseller or purchaser. Before installed you can modify it with impunity
And they are only considered federal property “for the purposes of” charging someone who purposefully damages it or steals mail from it (ie. federal crimes). It is NOT federal property for any other purpose. There are no federal penalties for a neighbor who accidentally backs into it. It is STILL the property of the purchaser forevermore. I can still UN-install it and throw it away if I wish. For example, I can buy a new one that I like much better, and I do not have to get the permission of the federal government to do so.