Duplicate email notification were sent from the instance when it was not intendedIssue Duplicate emails sent to the same recipients for the same record CauseAn Out of Box (OOB) business rule 'Ignore duplicates' will prevent duplicate email notifications from going out when 2 emails have same set of recipients and are meant for same target record. It is possible that duplicate emails get sent out if this business rule is customized or there are other custom business rules on the sys_email table that have a similar logic.ResolutionRestore out of box (OOB) 'Ignore duplicates' business rule and test the functionality.