Go to Site > Communications > Message Templates, and select Applicants tab.  Click on the "General or Conditional Applications Reverted to Drafted" communication.  Make changes as needed, including the Deliver When field.  Click Update Message Template.

This communication can be triggered by direct or indirect actions on part of the Applicant or an Administrator.  As applicants might not be aware of these actions, utilizing this email may be helpful as a notification to resubmit/complete their application.