First of all, I like the simple interface, very straight forward.
Adding a domain is easy and adding the DNS records is also very easy.
Did some testing with 4 domains, one of my domains was blocked by my own firewall (Configserver CSF, set block SMTP to off).

I use it as a Sendgrid alternative and works like a charm. The developer reached out and is very responsive. I gave some suggestions and also got a very quick response.

I am giving 4 taco's because still room for improvement, maybe a bit more documentation.