Registration via Snail Mail

Yesterday, I went to bank to convert check into money. Then I was said it costs 2,100yen(about $20) per each check. So I stopped to convert. Oh my! I didn't know that it cost too much. Now I stop accepting check. I don't have any idea. But I heard 'Money Oder System' can send money which is handled in Post office. I don't know detail. I received an email that says he send me cash a month before, but I never received it. I think it is very dangerous sending cash. You don't do so. If you have any idea, please let me know.