The System Property 'Allow using of IP address in MX records' is disabled, however MX records for the newly created domains do still point to IP addresses.
The System Property 'Allow using of IP address in MX records' only takes effect during manual DNS record creation by a customer. It is not taken into account during automatic DNS record creation during a service assignment. In such cases information from the corresponding (Qmail or Exchange) service branding is taken.
Edit Qmail or Exchange hosting branding configuration at Top > Marketing Director > Branding Manager > Brands > cp.vendor.com > Service Branding and set appropriate distinguished name.
See alsoBranding Qmail -- POA Providers Guide, page 340
Branding Exchange -- POA Providers Guide, pages 341-367