I used eM Client a few years ago, but eventually, I went back to Thunderbird.
Recently I decided to give it a try again and the experience is much better!
So much better that is now my default client again. You are doing a great job, keep it up!
Even memory resources are better than Thunderbird: eM takes about 100mb whereas Thunderbird at least 200 or more.
The UI looks neat and clean. But other than the interface, the overall experience is a pleasure.