First E-Mail arrives, Display on.
Later, i switched display manually off after using Facebook and WhatsApp. A few seconds later E-Mail arrives, display didn't get on.
Going back to 1.2 until it's clear what causes this.
Maybe i should write how i think this should work:
Notification arrives, display is off, sensor uncoverd => display should light up immediately, unless App is blacklisted/not whitelisted, even display was switched off 5 seconds ago.