Really nice to see some innovation in this space. I have used a particular provider since 2006 and eventually ripped out 98.5% of their system to replace with my own, but am familiar with the offerings you're competing with. Most are godawful. They're largely bubblegummed-together, the reporting is atrocious, they're virtually unusable by the (surprisingly) non-technical people who have to work with them, they have UXes which actively discourage customers' customers from spending money (!), etc etc.

I would not be surprised if the market eventually pushed you into handling fulfillment, by the way. For many of the early adopters in this space that's as simple as "proxy a download link and send two emails" but it's a really important part of the puzzle for them.