https://raspberry.tips/raspberrypi-einsteiger/raspberry-pi-im-internet-absichern-eures-mini-rechners

for unattended-upgrades, update-notifier   customize:
   /etc/apt/apt.conf.d/10periodic
   /etc/apt/apt.conf.d/20auto-upgrades
   evtl. /etc/apt/apt.conf.d/50unattended-upgrades, 
       in "stretch" change delivered file ! see:
       ( https://raspberrypi.stackexchange.com/questions/72022/configuring-unattended-upgrades-on-raspbian-stretch )

for mails see https://blog.dantup.com/2016/04/setting-up-automatic-updates-on-raspberry-pi-raspbian-jessie/