Why is a user receiving duplicate email notifications in Vault?
The user is receiving two different emails. One is a Task Reminder Notification,. The other is a Task Over Due Notification configured on a Document workflow step.
Task Reminder Notification - This is a Job that is set up to run daily at 5:00 AM. It utilizes the task_reminder_notification__v Document Message.
Task Overdue - This is the notification being sent from the workflow step to notify the user the task is overdue. This utilizes the task_overdue__c Document Message.
Vault Workflow Documentation: Configuring Document Workflows: Workflow Task & Decision Steps