A smart I.T. person could write a scraper program to pull liens from online sources, and search for corresponding properties that have active triggers, like an NOD.

What is the probability of a bad happening, and corresponding effect of that bad?

I have read with these types of people you can send a letter stating all correspondence must be done with mail unless an emergency arises.

When a tenant is willing to correspond via email it can help with language barriers (google translate isn't perfect, but it can certainly bridge a gap).

Thank you very much for your advice and I look forward to corresponding in the future.

If you are in cash flow property that has been properly researched and executed and you have a long term perspective, you are likely to be well positioned to weather a storm and in fact could benefit greatly from the corresponding fallout.  

I don't think there's much one can do to change that mindset, but allowing emotions to cloud judgement and engaging in less than professional correspondences will only perpetuate the myth of the "greedy, evil, rich landlord".

When I look at flips I can sometimes correspond the tile in the house to a period of time long past.....meaning it's dated.  

As far as proving it, I've been wondering if email correspondence counts. 

All of the correspondence going to the deceased and heirs are being send to the same property.