I once knew how to do this but I seem to have misplaced the information. I need to look up which domain names are all pointing towards nameserver "X".
If you do not want to make the information public you can also PM it to me if you like.
The reason I need to do such a lookup is that I'm going to take a server offline that was my very first server and has been in operation for almost 3 years. During the first 1.5 years running as the primary DNS for all servers as well as hosting sites.
Before February 12th I'm going to take this (now old) server out of service but I know several domains on the other servers still use the DNS of this server. I don't feel much inclined to look up a thousend sites in the whois database to see if they still use this server for DNS but I also wouldn't feel too happy about a couple of dozen sites going offline when I shut down this server
Your help is much appreciated.