I received what appears to be a very official form in a business type envelope with bold lettering on the outside stating PROPERTY TAX INFORMATION ENCLOSED. (in another portion of the envelope in a little box are the words "This is not a government document. Postmaster, if undeliverable, do not forward). That is a clue, but the letter inside is pretty formal in wording and states that due to recent changes in "market values" my property taxes may be higher than what the property is worth, and for a "fee" of $189 they will "review" to determine if I could benefit from a "reassessment", which could "result in a tax savings of $1, 462.50 annually."
Needless to say, I was aware this letter is a scam and phoned my local tax assessor's office and they referred me to our State Dept of Justice, who is collecting evidence against these scammers.
People need to be aware that your local tax assessor will reassess your property FOR FREE if you request it. Those who are not aware of that may fall for this scheme and pay $189 to someone who can do NOTHING for you.

Another clue that these guys are crooks, my property is in OREGON and the scammer's letter comes from CALIFORNIA. So, other states may get involved too.