11/3/17: The vast majority of popular prepaid debit cards are now blocked via a register hardcode at most locations.

This is the thread for 2017. The previous discussion can be found here.

Newbies: READ for days and learn before trying. It is best to know what you are doing, so start slow. Refer to cards as "Debit" not gc.

"Money orders can be purchased at any Post Office™ location.
Pay for your money order with cash, debit card, or traveler’s checks."

Fees:
$0.01 to $500.00: $1.20
$500.01 to $1,000.00: $1.60

Most post offices allow split payment (multiple debit cards) for one money order up to a max of $1000.

Example of how to split payment:

1. "One MO please for $998.40. Id like to pay with 2 debit cards, $500 on each."
2. Swipe first card and enter pin.
3. Remind teller that its "$500 on that card". They will change the amount on their screen to $500. Transaction goes through and a small receipt prints.
4. Swipe 2nd card, enter pin.
5. Done.

Note: If you encounter a problem with the second card and have to cancel the transaction, it can be very difficult to recover your funds on the first card. Always have a back-up payment method available (bank debit card or cash).

GC Information: The fine print on the back of the package shows the bank issuer. Don't buy GCs with tampered packaging and always use cards ASAP.

Visa OneVanilla and Vanilla GC issued by Bancorp work at PO.

Visa/MC Gift Cards issued by MetaBank have not had any success at MOST USPS anywhere in the country since around September 2016.
These will NOT work if the clerk uses a touchscreen
These MAY work, and often do, at small, rural post offices where clerks do not have touch screens.

Visa Gift Cards from Walmart issued by Green Dot have stopped working for MO purchases for some.

GAME MOSTLY OVER, MOST USPO are HARD CODED to NOT ACCEPT NON BANK DEBIT CARDS
Exception seems to be small, rural post offices where clerks do not use touch screens.