I don't believe there is anything illegal about filling a prescription that was legally obtained by a licensed physician via us mail. In fact, a lot of insurance companies now offer order by mail, so there is nothing 'wrong' with ordering/sending/receiving an Rx via the mail system. Perhaps there is something you're not aware of- I seriously DOUBT that the PO has any idea whether that came from a mail order Rx company or an OP. I'd go talk to them- my guess, nothing at all to fear