Zwave Plus device in outdoor metal box not reliable

We’ve installed a lot of mailbox sensors. Monoprice used to make an excellent Mailbox sensor, unfortunately they’ve discontinued that. You can still use some good sensors from other brands, just make sure they’re Z-Wave Plus to being with, they have more sensitive antennas and lower power with longer range.

First put a Z-Wave Plus Repeater on the outside of your house, with direct line of sight to the mailbox.

I would not recommend Levitron Z-Wave devices, we’ve seen all sorts of issues with them for many years now. There are many other better brands that do a better job as Z-Wave Plus repeaters.