I was in LE for around more than 2 decades. Not once, in any of that time, could I get the US Postal Inspectors office to take action or even assist in a mail fraud case.
I had many cases valued in the 10s of thousands and 2 in excess of $100,000 and the postal inspectors had absolutely no interest in doing anything to prosecute or assist in prosecution. I had one fraud in which an 80 year old woman sent $38k to a real address in NOLA.
We found out about it the following day when the woman's daughter heard about it. It was sent overnight USPS and we had delivery confirmation at the residence.
NOLA detectives went to the house, knocked on the door and when the door opened, they saw the packaging materials sitting on the coffee table in the living room area.
The guy gave a full confession and said he had done it dozens of times. He was paid by an "unknown" person to receive the packages and deposit the money.
He would then take the money down the street to a bank and deposit the money in several different accounts. All of this information was verified except, that it was an "unknown" person running the scheme. I am sure he knew exactly who was doing it.
Anyway, after the money was deposited, within a few minutes, it was removed from the account and disappeared. We never got that money back for the woman. The postal inspector refused to participate in the investigation and, as far as I know, nothing was ever done. They are the laziest, most useless government organization we have.