Hi,
I just discovered this client & it seems very nice, however I noticed it lacks one important feature for me:
I play a lot video games when I’m spending my time at PC, but I also need to check mails soon. So instead of minimizing game, opening a browser or email client & check either I have new mail or not isn’t good option. Especially if I’m waiting for important mail. So, I need email client which will make sound when new mail arrives, even if I’m in a game. If developers could add option, regarding application is active or not, it could still give us sound notification, it would be great. Right now I switched to Thunderbird, cause it still makes the sound while I’m gaming, but I’ll switch back to eM Client, if you gonna add this feature 
when you go to: tools ->settings and click on “notifications” you will find the sound file for incoming mail. you can replace the existing one with any sound file you have or can download from the internet.
I know that. I wrote completely different thing.