I am seriously interested in your product but I absolutely have to solve the configuration problems.
Yesterday I downloaded eM Client for Mac (Mac BookPro - OS X El Captain) and installed but I’ve got problem with particular settings of my provider.
I use a provider (Register.it) that has specific security features and in the attached image you can see its requests.
Below you see the eM Client test result.
It is clear that I must first resolve the problem in order to buy your product.