I would be very interested in using this 1 year ago, but now I'm gladly out of the email business. Although Mailgun is great, it is still email.

I'm now more interested in your business model. How are you doing with selling an open-source software as a service? Also, isn't your price too cheap? (I'm saying that because I'm doing the same thing with https://github.com/fiatjaf/trackingco.de and my prices are also very cheap, such that the growth hackers out there would be prompted to say incessantly: "raise your prices!")