DNS & Glossary

PTR record (Pointer / Reverse DNS)

The reverse of an A record: it maps an IP address back to a hostname. Mail servers check it, so a correct PTR is important for email deliverability.

What it stores

A PTR record lives in a special reverse zone (in-addr.arpa for IPv4, ip6.arpa for IPv6) and maps an address to a name. Reverse DNS is usually controlled by whoever owns the IP block — often your hosting provider, not your domain's DNS.

ZONE FILE
34.216.184.93.in-addr.arpa.  3600  IN  PTR  mail.example.com.

Why it matters

  • Receiving mail servers reject or downrank senders whose IP lacks matching forward and reverse DNS.
  • It aids diagnostics by attaching a human-readable name to an IP.

Common mistakes

  • Missing or mismatched PTR for a sending mail server, hurting deliverability.
  • Assuming you can set PTR in your own zone when the IP owner controls it.

How WebInspect checks this

  • The Network Inspector performs reverse-DNS lookups and reports the PTR alongside forward-confirmation checks.