Oh really? CoD? Please teach me, oh great master, cause even Anet stated that there is no such option.
The general idea that Anet went with with regard to trading is to create two environments for trading: one within trusted circle and second outside of it to avoid scams and needles GM intervention. Trading Post is the secured way to sell and buy goods from people you don't know and can't trust without fear potential scamming. Mail is sending and receiving from trusted group of people. There is no CoD option and not going to be ( t least according to Anet blog post about it) since you only supposed to use it as you have been - among friends. What people are doing right now, spamming WTS on map chat is ripe for scamming since you can only hope that the other side will fulfill their end of the bargain and that's why Trading Post is so important - it's a security issue most of all.