“Domain already exists” error while adding addon domain in cpanel

problem :

Domain already exists

Solution :

#/scripts/killdns domain.com (where domain.com is the name of the domain you are trying to add in cPanel)

These are the locations to search for any reference to domain.com

/etc/named.conf
/usr/local/apache/conf/httpd.conf
/var/named/domain.com.db
/etc/userdomains
/etc/localdomains
/var/cpanel/users/

sumber : http://kb.veeble.org/%22Domain_already_exists%22_error_while_adding_addon_domain_in_cpanel.