Version: (using KDE 4.1.3) OS: Linux Installed from: Ubuntu Packages There doesn't seem to be a setting that allows kontact to be closed to the system tray. This means it has be restarted (with the concomitant tedious delay) frequently, instead of just being re-activated with a click on the system tray. (Compare this to the behaviour of kontact and amarok, for example).
There is an option in Kmail/Settings/Configure/View/Kmail on the System tray tab. Though from KDE4.2.8x it doesn't work correctly for me, if I choose "Only show Kmail in system tray if there are unread messages" option and close Kontact (not Quitting, simple just close the window), I won't be able to switch it back again (Kontact seems to be running but no system tray icon any more).
*** This bug has been marked as a duplicate of bug 75446 ***