# What is a PTR Record? Reverse DNS Lookups Explained > A PTR record maps an IP address back to a hostname for reverse DNS. Learn how PTR records work, why email servers require them, and how to set one up. A PTR record (Pointer record) is a type of [DNS (Domain Name System)](/learning/what-is-a-dns) record that maps an IP address to a hostname, enabling reverse DNS lookups. Most DNS records translate names to addresses — an [A record](/learning/what-is-an-a-record) turns `mail.example.com` into an IP. A PTR record does the opposite: it turns an IP back into a name, so a server can check what hostname claims ownership of the address that just connected. That reverse check is a foundational trust signal for [email authentication](/resources-post/what-are-dmarc-dkim-and-spf) and helps mailbox providers screen out [spam](/learning/understanding-spam-emails) and [spoofing](/learning/what-is-spoofing). ## How does a PTR record work? PTR records live in a special reverse-lookup zone: `in-addr.arpa` for IPv4 and `ip6.arpa` for IPv6. The IP's octets are reversed to form the record name. Here's the lifecycle: - **Record creation:** the owner of the IP address — usually your ISP, hosting provider, or cloud platform, *not* the domain owner — creates the PTR record in the reverse zone. For the IP `192.0.2.1`, the record name is `1.2.0.192.in-addr.arpa`, pointing to a hostname like `mail.example.com`. - **Reverse lookup:** when a receiving mail server sees an inbound connection from an IP, it queries the `in-addr.arpa` zone and gets back the PTR record's hostname. - **Forward confirmation:** the receiver then does a *forward* lookup on that hostname to confirm it resolves back to the original IP. This round-trip match is called **Forward-Confirmed Reverse DNS (FCrDNS)**, and it's what turns a PTR record into real evidence of legitimacy. - **Application:** the result feeds spam filtering and complements [SPF](/learning/what-is-spf), [DKIM](/learning/what-is-dkim), and [DMARC](/learning/what-is-dmarc) checks on the message itself. For example, a matching FCrDNS setup for `192.0.2.1` looks like this: ``` 1.2.0.192.in-addr.arpa. IN PTR mail.example.com. mail.example.com. IN A 192.0.2.1 ``` The PTR points the IP to a name, and the name's A record points back to the same IP — the loop that receivers require. ![A PTR record and its matching A record, forming a valid Forward-Confirmed Reverse DNS (FCrDNS) loop.](/images/figures/what-is-a-ptr-record-fig1.webp) ## Why PTR records matter for email Reverse DNS is no longer a nice-to-have. Under the [Google and Yahoo bulk sender requirements](https://blog.google/products/gmail/gmail-security-authentication-spam-protection/) that took effect in **February 2024**, senders must operate from IP addresses with valid forward and reverse DNS — a working PTR record with FCrDNS is explicitly required. Beyond that mandate, PTR records deliver several benefits: - **Acceptance:** many mail servers reject or heavily penalize connections from IPs with no PTR record at all. - **Deliverability:** a clean, matching PTR signals a legitimate mail server and helps you clear spam filters. - **Reputation:** missing, generic, or mismatched PTR records look like compromised or dynamically assigned hosts and drag down [domain and IP reputation](/learning/what-is-an-ip-reputation). - **Troubleshooting:** PTR records make it far easier to identify servers in logs and security audits. ## How to check a PTR record You can look up any IP's PTR record from your own machine: - **macOS / Linux:** `dig -x 192.0.2.1 +short` returns the hostname, or `host 192.0.2.1`. - **Windows:** `nslookup 192.0.2.1` shows the reverse-mapped name. To confirm FCrDNS, run the reverse lookup, then do a forward lookup on the hostname you get back and check that it returns the original IP. If the two don't agree, the loop is broken. For a quick browser-based check without the command line, run the address through our [DNS lookup tool](/tools/dns-lookup), and verify the rest of your sending setup with the [Email Security Score](/tools/email-security-score). ## Things to keep in mind Setting up and maintaining PTR records takes attention to detail: - **Your host controls it.** Because the IP owner manages the reverse zone, you usually request or set the PTR through your hosting/cloud provider's control panel, not your normal DNS editor. - **Keep FCrDNS consistent.** The PTR hostname must resolve back to the original IP via an A or [AAAA record](/learning/what-is-an-aaaa-dns-record-quad-a-explained). A broken loop causes authentication and deliverability failures. - **Use a meaningful hostname.** Generic names like `server1.hostingcompany.com` or anything resembling a dynamic-IP pattern are treated as suspicious. Yahoo explicitly asks for non-generic reverse DNS that reflects your domain. - **Align with HELO/EHLO.** For mail servers, the PTR hostname should match the name used in the [SMTP](/learning/what-is-smtp) HELO/EHLO greeting and your SPF setup. - **PTR is a supporting signal.** It doesn't stop spoofing by itself — pair it with SPF, DKIM, and DMARC for real protection. ## Frequently asked questions ### Who is responsible for setting a PTR record? The owner of the IP address — typically your ISP, hosting provider, or cloud platform. Unlike A or [TXT records](/learning/what-is-a-txt-record) that you manage in your own DNS, the reverse zone belongs to whoever controls the IP block, so you request the PTR from them. ### What happens if my sending IP has no PTR record? Many receivers will refuse the connection outright or route the mail to spam. Since February 2024, sending to Gmail or Yahoo without a valid PTR and FCrDNS puts high-volume mail at real risk of being blocked or filtered. ### What is the difference between a PTR record and an A record? An [A record](/learning/what-is-an-a-record) maps a hostname to an IP (forward lookup); a PTR record maps an IP back to a hostname (reverse lookup). For email, both should agree — that mutual match is FCrDNS. ### Can one IP have multiple PTR records? It can technically, but you shouldn't. Best practice is a single PTR per IP pointing to one meaningful hostname. Multiple or conflicting PTRs create ambiguity that receivers may treat as suspicious. ### Do PTR records work for IPv6? Yes. IPv6 uses the `ip6.arpa` zone instead of `in-addr.arpa`, with the address expanded into reversed nibbles. The FCrDNS principle is identical: the PTR hostname must resolve back to the same IPv6 address. ## Related reading - [What is an A record?](/learning/what-is-an-a-record) - [What is a TXT record?](/learning/what-is-a-txt-record) - [What is an IP Reputation?](/learning/what-is-an-ip-reputation)