MailItem.ToDoTaskOrdinal Property (Outlook)
Returns or sets a Date value that represents the ordinal value of the task for the MailItem. Read/write.
This property returns Null (Nothing in Visual Basic) if the IsMarkedAsTask property is set to False.
This property is used to indicate how the task should be ordered within the parent groups, such as the Today group or the Tomorrow group, of the To-Do Bar. The value used in this property does not have any relation to the values of the TaskStartDate, TaskDueDate, or TaskCompletedDate properties.