Send NOTIFY to other then NS Servers.
When using Slave/Secondary/Backup Hosting elswhere. Often the Transfer & Notify are not sent to the Nameservers in the NS Records. The AXFR Whitelist solves the Zonetransfer. But as far as i can see NOTIFY sill gets sent to the Nameservers in the NS Records.
As a side note, is there any plans to implement TSIG ?