Reyner,
Maybe I'm confused as to what you mean by "reseller's domain".
Do you mean your own reseller account, from your admin user?
If so, then there is no "reseller's domain"; there's the server name under "Admin Settings" and the user domain in the Reseller's User panel.
Or do you mean the domain name assigned to a reseller you've set up on the server?
If so, then you find that in the Reseller's User panel.
Jeff