Many financial institutions, including mine, have been burned by fake Postal money orders and put an inordinantly long hold on them. Basically if the MO comes back as fake after presented to the counter party, which can be weeks later, you are on the hook, as is the case with personal checks, certified checks, etc.
Your first suggest, presenting to the USPS, is best, since they can verify that the MO is legit and you walk out with your cash or new MO.
Your first suggest, presenting to the USPS, is best, since they can verify that the MO is legit and you walk out with your cash or new MO.