Just re-reading this old thread I wonder how the first NOTIFY should be sent? The NOTIFY needs some route headers to sned the first notify.
Thus, I suspect that the notifier should use an "early route set" to send the first NOTIFY (learnt from the RR headers in the SUBSCRIBE) and further NOTIFYs should use the route set learnt from the RR headers in the response to the first NOTIFY.
Is this correct?