There are some International Money Orders that the Post Office will cash and there are some that the PO will not cash and you end up having to take to your bank and quite likely pay a fee on. (and of course there's the whole chargeback risk, which the PO would also come after you if it's bogus.)
Of course, Intl MO must be payable in US Dollars.
List of Countries That Will Issue International Postal Money Order That The USPS Will Honor
max value of money order is $700 USD unless otherwise noted
Albania
Anguilla
Antigua and Barbuda
Bahamas
Barbados *
Belize
British Virgin Islands
Canada
Dominica
El Salvador ($500 max)
Grenada
Guyana ($500 max)
Japan **
Montserrat
Peru
St. Christopher (St. Kitts) and Nevis
St. Lucia
St. Vincent and the Grenadines
(*) In Barbados the amount of the money due for payment will no longer be handwritten on Form MP1 (the form currently states "Amount To Be Written In Words") but will be electronically applied.
(**) In Japan the Form MP1 money orders issued for payment in the United States must be shown in U.S. dollars preceded by the capital letters "USD."
Hope this helps