this isn't the airtight solution you're looking for, I would guess, but in the past I've kept receiving at the same spot after like 4 love letters. all were for very small amounts tho, which I'm sure played a role.
if you can join in some kind of community that has its own building, and where many receive mail; like a university or maybe an upscale gym? (lol I have no idea I've never been to a gym) or maybe a vfw or the rotary club. idk the hassle seems enormous but I've always felt parcels sent to a rotary club would always land.