Issues Associated With Generic rDNS

TQMcube is currently listing appoximately 45,000,000 IP addresses as dynamic.

Nobody should be sending email direct to MX from a dynamic IP. No competently administered mail server should accept email from a dynamic IP. The probability that email sent from dynamic ranges is spam is nearly 100%

Generic rDNS means that a DNS query on the IP address resolves to something like: 123-45-67-8.your.isp.com. The opposite of generic rDNS is a “unique reverse pointer” which is usually something like “mail.your-domain.com.”

There is a high potential that DNSBLs will identify a generic host as dynamic. Many mail servers are similarly configured. While the word “static” in the generic host name will usually prevent a DNSBL listing, it still depicts a lack of professionalism.

Someone in the range has to send spam for TQMcube to list the /24 as dynamic. There is nothing gratuitous or arbitrary in our listings. It doesn't seem unreasonable to suggest that a competent administrator should offer the accountability provided by a proper reverse pointer without having to query whois.

For the vast majority of these generic hosts, a whois on the IP points to the provider anyway. This is compounded by the fact that very few ISPs are responsible enough to provide or publish their dynamic ranges.

The bottom line:

1. If you have a static IP then you should have a unique reverse pointer.
2. When obtaining or changing providers, a unique pointer should be a requirement.
3. It is now trivial for an ISP to provide a unique reverse pointer. If they will not do so then you need a different ISP! There should be no cost for a pointer.
4. If you already have established static service then your ISP should provide a pointer. Most will do so within an hour or so of a request — but you have to ask.
5. If nothing else, a unique reverse pointer looks more professional.