I have installed deb64 package on Ubuntu 16.04, the app works well, but I can't make it exit. The "X" button at the top of Zoiper window just minimizes it, right click on sidebar and choosing "exit" from the menu does the same. There is no exit option anywhere else in the app. The only way I was able to exit was to open the terminal and type "killlall zoiper", but it doesn't seem to be user friendly enough.