Postal money order?

There is a big difference between a United States Postal Money Order which is backed by the US government and a normal money order that one would obtain at a bank or elsewhere.
To me a USPS money order is as good as cash. When I have received them I cash them at the post office and use a portion of the cash to paid for the postage of the item I sold - Perfect.
A regular money order I treat as a check & wait for it to clear the bank.