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?
The PTR DNS records in the reverse DNS can be used for several things.
The first - use a FCrDNS verification, in case of valid domain - add it to "Received:" trace header field.
The second - perform FCrDNS verification on the domain name given in the SMTP HELO and EHLO commands.
The third - check reverse domain name if they are look like from dial-up users, or some dinamic IP address.
And the fourth - check for domain name is owned by same person as domain from ptr record.
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.
Only ISP that own IP address cat set or remove PTR record, nobody other can do it, user that using current IP can't do it too.
Ptr test available with short link: