If you are manually configuring other nameservers to be secondaries for domains created using Virtualmin, you should add their hostnames to this text box. This will ensure that the required `NS` records are added to the DNS zone, and that the secondaries are used.

If you have configured Webmin to automatically create slave domains on secondary nameservers, their hostnames do not need to be entered here. Instead, Virtualmin will add them to the DNS zone automatically.