Love the native idea, but then I clicked on the pricing link - woah. I'm by no means telling you how to run your business, but the pay per email rates seam really high.
I wrote an email marketing system this week for my day job against the Mailgun API to do the sending and to send to 183k recipients, it'll cost us < $80 USD. It would be even cheaper if I used AWS but we're a Rackspace shop.
(I understand not everyone out there is a programmer, but the price is very high compared)
Good luck though.
