2GIG-TILT1-345 as mailbox sensor

Can someone please tell me the range of the 2GIG-TILT1-345 sensor? I am interested in using it for a mailbox alert. Can you put an external antenna on it if the mailbox is metal? Is there a better unit to do what I am trying than this one?

Open air range is about 300 feet. Realistic range is lower. If the mailbox is metal I would not recommend installing an RF sensor inside as the range will be severely affected. I wouldn’t recommend trying to DIY an antenna. Instead you could use a wired door sensor and run the wire to a wireless transmitter with a wired input designed for outdoor use like the DW30 or the Honeywell 5816OD

I have a metal mailbox inside a brick structure about 150 feet from my IQ4 panel. Signal has to go through 3 walls, brick, then the metal enclosure. I have a legacy 2gig wireless window sensor DW-10 that has an external magnetic contact through the external inputs built into that sensor. Everything is inside the mailbox.

It has worked fine for years.

Not saying yours will work, but it does seem possible