Single risk notifications are configured within the Symantec Endpoint Protection Manager (SEPM). When a single risk notification is generated, it sends an email for the same event approximately once every three minutes. The insert time for the event in the database is the same in every email.
This problem is fixed in Symantec Endpoint Protection (SEP) 12.1 Release Update 2 (RU2). For more information on obtaining the latest version of SEP, see Obtaining the latest version of Symantec Endpoint Protection or Symantec Network Access Control.
If it is not immediately possile to upgrade, a workaround has been identified:
Observed with fresh install of SEP 12.1 RU1 MP1. Embedded database.