You will need to set up maintenance email alerts, there is a section dedicated to that here:
1.8 - Xibo CMS Post-Installation Setup Guide
1.7 - Xibo CMS Post-Installation Setup Guide - 1.7 Series
email alerts / recovery emails are sent on transition between logged in / out status of the display during maintenance run (every 5 min by default) according to either global timeout or collection interval depending how did you configure that for a display.