This project looks like a wrapper over andris9/simplesmtp, and should be advertised as such instead of a smtp implementation. Check out <a href="https://github.com/baudehlo/Haraka" rel="nofollow">https://github.com/baudehlo/Haraka</a> for a mature smtp project instead of a wrapper.
This is really great. Plus I love the attention to detail in the documentation, and how the demo worked right away. We currently use Mailgun for this but I would love to switch over to using Mailin and host it ourself.