USPS nationwide policy prohibits the use of credit cards for buying money orders. Policy DOES allow the use of ATM-only cards (remember those? LOL) or debit/checkcards iff used as a PIN/debit/ATM transaction. BofA will somehow disallow miles from such transactions.

However, there are, uh, other merchants that are "Money Service Businesses" or provide money services (money orders, funds wire, bill payment etc) that take debit cards...and you still get miles.

Western Union, for example, lets you wire money or make payments (car, house whatever) via credit/checkcard over the phone or internet. Since most credit cards will charge you a cash advance fee (and thus negate your miles) for such a transaction, your checkcard is a better solution: no cash advance fee AND you're 99% sure to get your miles. But there is the WU fee. But if you have to wire $3,000 bail money to spring granny anyway, you may as well get some miles for it

Note that for any of these businesses you're may have to fork over some information for large (>$900 to $3,000 depending on the company) because of the ew USA Patriot Act, the Bank Secrecy Act and other federal laws governing money laundering etc.