I am trying to see all the emails, where the delivery status was "unknown". I have been trying to change the URL parameter "delivery_status_value" to "unknown", but that gives a fail as a response. Which value should I use for querying? Or is there another way of filtering the recipients, which's delivery status is unknown? I would have downloaded the excel/CSV file, but that does not seem to work on our system.
The version we use is 4.6.36.
Thank you very much for your help!