It’s about being smart, skeptical, and a bit of a detective work. 

The tenants were understandably concentered about the possibility of mold growth resulting from the water intrusion, so I had a test done which detected some mold.

With technology and on line title records, major loan servicers are set up to detect deed transfers in major counties.  

this is the most transparent scammer outthere, i am actually very worried about OP if they can't detect this easily, he is selling mortgage, oil, insulin and tax services in one hospital out of ohio somewhere...come on...

There is a new smoke detection unit that has been appearing on my facebook feed which also does noise detection and is being marketed towards STRs.

Not sure if the answer isa) nothing I can do about it, b) put a wireless water meter to help detect leaks on it (how does this work for a rental where the internet is theirs?)

I use these:LEPOWER LED Security Lights Motion Sensor Light Outdoor, 38W 4200LM Light, 5500K, IP65 Waterproof, 3 Head Detected Flood for Garage, Yard, Porch (White) - Amazon.comWhen flipping out of state I go Simpli Safe.When it comes to local flips I have a home security contracting company that has their own alarm system and app that I really like so I use them but they are local to Cleveland. 

Perhaps there is one, but until that can be provided as justification for their decision it doesn't seem proper for USPS to be playing 'detective' telling people they can't hang a mailbox when there is a physical address on record with the county.Has anyone run into this too?

It is not worth the time or effort IMO to be a private detective. 

But I would not let him out due to a smell only he can detect.