This is tool for domain ptr lookup
, it's working for domain name and email address.
going in two steps: first - lookuping domain's IP address and seconde - resolve domain name (canonical name) for currect IP.
PTR - Pointer to a canonical name. It's different then CNAME, because DNS processing does NOT proceed, just the name is returned.
A PTR record is opposition of an A record. A records resolve domain name to IP address. PTR record resolve IP address to domain name.
Why check ptr
is important part of anti spam checking?
For example IP addresses (like 184.108.40.206) is assigned by a central organization to some fixed ISP.
An ISP that 'owns' an IP address can give it to use for some customer, and only this ISP can register a DNS record that - IP address 220.127.116.11 corresponds to the server 112.example.com.
Note that only the ISP can do this, not a customer that using this IP during now.
This is called "reverse" record, because as usually DNS records looking like name to IP address, but we see that it's IP address to name.
Ptr testing and ptr record lookup used by AOL, for example AOL denied to send mail from IP without PTR record: "AOL may no longer accept connections from IP addresses which no do not have reverse-DNS (PTR records) assigned."
This ptr record lookup tool created for ptr record check, because it can be useful for webmaster and admin in case of email delivery troubles.
As usually email server checking ptr info for find any ptr, in case of record exist - check success and email have chance to be delivider.
Ptr test available with short link: