If you send a postal money order to me, I go to the post office. They check to see if the MO is legit before they even cash it. If it’s not, I keep the parts, walk away and deal with you about the bogus MO. I’m not out the parts. If they cash the MO, even if it is bogus, I get the money, and the parts are sent. There is no recourse for the post office to come back on me, it’s not tied to my bank, I have cash in hand and the parts are sent.
Now, if I go to the bank with a bogus cashiers check and they don’t catch it right away and either cash it to me, or I deposit it in my account, I may walk away thinking that it was legit. It could take the bank 2 weeks or more to find out that it was bogus, and they have recourse to take the money out of my account, whether or not I deposited it. Unless you go to a bank that the cashiers check was directly issued from and cash it, you are forced to run it through your own bank. Now, if you’ve waited 2 weeks for the check to clear, and you send the parts, and the next day they find it’s bogus, you’re out the money and the parts.
My personal preference is to receive postal money orders only. It’s like having a bank in every town, and it’s not tied to your bank, they can check it’s validity right there, and you either walk with the money and no ties to your bank, or you walk with the parts and don’t have to deal with the scammer at all if the MO turns out to be bogus. I don’t know a scammer in this world who would escalate the matter of a bogus postal money order. And, not to mention, that the post office is a federal institution, a bank is a private entity. Passing off a bogus postal money order is a federal offense, passing off a bogus cashiers check is a crime, but not a federal crime, and must be pursued by the cops, or the bank you transacted with, which will just withdraw the money they gave you and make you pursue it yourself. Got it?