The person assigned to the ticket automatically becomes a follower and receives notifications about changes in the ticket. Note that external users only receive notifications but cannot log in or view the ticket itself. You can also enable notifications for approaching and reached ticket deadlines. Notifications are sent to all the ticket's participants, assuming the relevant Workflow settings listed below are enabled in the Radar Security Center settings.
Settings > General settings > Workflow
Notify participants when deadline has passed
Number of day(s) before deadline to notify participants about it
Note, that changing these fields does not trigger a notification: