Server include four mode : eg: domain name : www.bbb.com
mode 1:www.bbb.com use ptr to point to www.bbb.com
mode 2:bbb.com use ptr to point to bbb.com
mode 3:(www.)bbb.com use ptr to point to bbb.com .and add string www.to front bbb,com manually
mode 4:www.bbb.com not use ptr