Left mouse button click on system try icon

I just upgraded to the current mailspring release.
I used to click on the system tray mailspring icon with left mouse button and mailspring window popped up showing inbox folder. Then I click again on the same sys try icon and mailspring window disappeared.

Now with 1.10.3 version, if I click on the icon it present a menu, the same menu that appears by clicking with right mouse button.

I just upgraded my whole linux system from slackware 14.2 to the new 15.0. So I cannot tell if this behavior is due to mailspring or to something broken on my system.

What should happen by left-clicking on the systray icon?

Thanks in advance!