It has got some really great response so far but I'd still like to ask more feedback about the software. Would be great if you could list some must-have features that such a software should have and can't do without.
The software is self hosted which means it requires some tech knowledge to set up (requires Node.js v5.0+ and MySQL v5.5+/MariaDB). I want to make setup easier in the future but at this stage there's only an installation script for Ubuntu 14.04 to help to get started more easily, so you still need to know how to use command line.
I know my software can never be as good as Mailchimp's because you can't really beat 15 years and hundreds of people but the cost of free is a also a pretty good feature to have.