remove kobool mailer ip address from exclude black list (xbl)

Kobool was added to xbl at: http://www.spamhaus.org/
as it was listed in CBL at: http://cbl.abuseat.org/lookup.cgi?ip=154.6.115.157

The reason was the hostname was not set to xxx.kobool.com
Fix:
edit /etc/sysconfig/network
and set hostname to: main.kobool.com

restart the machine.