I recently had this ticket created against nzb-notify requesting for the ability to send a notification if an NZB wasn't added due to being caught in the dupe check.
I think this is a fantastic idea and i would love to help him out, but my question is: "How do i hook into this from the the extensions side of things?". Just a little nudge in the right direction is all I need
Edit: Ticket was deemed as not necessary; thanks for all your feedback & help on Github @hubug!