I would suggest to reverse the tray icons colors: it is yellow for no new emails and white for new emails. The eye is more catched on the yellow/no email state than on the white/new email state, I think it should be the opposite from a user experience point of view.
My SysTray’s background is white…
I was about to report that sometimes the icon in the SysTray get whitened out to near invisible but I see that that is a “feature”. An unfortunate colour combination, however.
The above comment is a duplicate of the one posted at https://forum.emclient.com/emclient/topics/minimizing-to-tray-and-icon-disappears