DNS PTR Record: Reverse DNS Explained
A DNS PTR (pointer) record maps an IP address back to a hostname — the reverse of what an A or AAAA record does. This is called reverse DNS (rDNS). When a mail server sees a connection from 93.184.216.34 and wants to know what name that address claims to be, it looks up the PTR record for that IP.
What is a PTR record?
Forward DNS answers "what is the IP for this name?" A PTR record answers the opposite question: "what name belongs to this IP?" PTR records do not live in your normal domain zone. They live in special reverse zones under in-addr.arpa for IPv4 and ip6.arpa for IPv6, and they are controlled by whoever owns the IP block — usually your hosting provider or ISP, not the domain registrant.
PTR record structure and example
To look up the PTR for 8.8.8.8, the IP is reversed and placed under in-addr.arpa:
8.8.8.8.in-addr.arpa. IN PTR dns.google.| Field | Meaning |
|---|---|
| Owner name | The IP address written in reverse and suffixed with in-addr.arpa (IPv4) or ip6.arpa (IPv6). Reversing the octets is what turns an address into a DNS name. |
| Type | Always PTR. |
| Target | The canonical hostname the IP resolves back to, e.g. dns.google. |
How to check a PTR record
# reverse lookup shortcut
dig -x 8.8.8.8 +short
# the explicit form
dig 8.8.8.8.in-addr.arpa PTR +short
# nslookup
nslookup 8.8.8.8To resolve reverse DNS for a whole address or discover which hostnames sit behind an IP, the free reverse IP lookup tool does it without the command line, and the DNS lookup tool covers the forward records for any hostname you find.
Why PTR records matter for email
PTR records are most important for outbound email. Receiving mail servers routinely reject or flag messages from an IP that has no PTR record, or whose PTR does not match the sending domain. The strong version of this check is Forward-Confirmed reverse DNS (FCrDNS): the IP's PTR points to a hostname, and that hostname's forward A/AAAA record points back to the same IP. If you run your own mail server and messages land in spam, a missing or mismatched PTR is one of the first things to check.
Common PTR record problems
- No PTR at all. Fresh server IPs often ship without reverse DNS. Outbound mail from them is widely distrusted until a PTR is set.
- PTR and forward record disagree. If the PTR says
mail.example.combut that name does not resolve back to the same IP, FCrDNS fails. - Trying to set it in the wrong place. You cannot add a PTR in your domain's zone. You request it from the IP owner (hosting provider), because they control the
in-addr.arpadelegation.
Related DNS records
PTR is one half of a matched pair with forward address records. Read the AAAA record guide for the IPv6 forward mapping, the SOA record guide for how a zone is defined, and the NS record guide for how zones — including reverse zones — are delegated.
Frequently asked questions
Who controls my PTR record?
The owner of the IP address block — normally your hosting provider or ISP. You typically open a request or use their control panel to set it; you cannot add it to your own domain zone.
Is a PTR record required?
Not for websites, but effectively yes for a mail server. Without a valid PTR (ideally FCrDNS-confirmed), a lot of your outbound email will be rejected or marked as spam.
What is the difference between a PTR and an A record?
An A record maps a hostname to an IPv4 address (forward). A PTR record maps an IPv4 (or IPv6) address back to a hostname (reverse). They point in opposite directions.