The automatically reported Incident emails can be turned off via:

• Settings → Company Edit → System Settings → disable the Send Incident Notification Emails toggle → and then click Save. 

You may want to use this setting if custom Incident email notification rules have been created via the Incident Rulebase. 

For more information, please refer to the following articles:

• What does Incident Rulebase do?
• Incident Rulebase - How do I create a Rule & Actions?
• Incident Rulebase - How to activate Incident Rules?
• Incident Rulebase Auditing