Today at lunchtime, one of my adult children came home to find a package containing something they'd ordered had been left by our back (kitchen) door. This is significant because in order for whoever left it to do this, they would have had to open a wooden gate in a high privacy fence and enter our backyard, something no mail or delivery person has ever done before. In fact, there was someone in our house all day, so if the mail carrier (USPS, in this case) was concerned about leaving it on our front porch, they could have easily rung the doorbell as they normally do. There was simply no reasonable excuse or reason for leaving the package where we found it, and someone clearly had to trespass to leave it where it was.
This is not our first serious incident with regard to mail delivery by any means. Indeed, much of our mail is delivered either wide open, damp from having been steamed, and/or opened and then crudely taped shut. In one memorable instance, a letter arrived having been opened and then glued shut again with what looked like white glue that had been applied so excessively that the letter inside was completely glued together as well! In another serious incident, a USPS mail carrier used a package containing something I'd ordered to try and get me to sign a mailing receipt for a package containing some kind of drugs or medications I knew nothing about and which weren't even addressed to me. (They were addressed to a business partner of my ex-husband's. The mail carrier tried to make me think I was signing for my package, but thankfully, I examined the card receipt first and then refused to sign it. I filed a complaint over this incident, but the USPS did nothing.)
No matter which carrier or delivery company is involved, the majority of our packages arrive with clear signs of having been illegally opened. Sometimes someone brazenly writes "Opened By Mistake" on these, but often they don't even bother. Also, I have a stack of mailing receipts over an inch thick for mail I've tried to send that has been lost or stolen (that USPS also refuses to do anything about).