Is there a performance advantage from using name to name comparisons instead of name to IP address checks?
It’s definitely quicker to do DNS lookups of the single, cached SURBL query than DNS lookups for Address and/or Name Server records for every web site in every incoming message. By comparing names to names in incoming URIs and SURBLs, we avoid a major performance bottleneck of URI checks that try to resolve wild domain names, whose name servers you have no control over, into IP addresses or NS records. In other words using a SURBL is much quicker.
