This depends on the amount of processing postfix is doing, but as a simple relay, Postfix should not raise sweat.
500 emails per hour is less then 1 a second. In terms of postfix volumes this is at least 2 orders of magnitude less you might expect to be able to handle on even a low end machine, so its easily doable. Depending on what you are doing though, make sure your systems are not constrained by very slow disk and that DNS is responsive.
Also, 12k emails per day does not typically equate to 500 per hour because it would seldom be the case that there are no peaks and troughs, but even so, you should be able to move 1000 times the envisaged volumes a day on a lightly tuned relay.