--- title: "Reverse DNS Lookup: Check PTR Records Free | Prosyo" description: "Free reverse DNS lookup: find the PTR record for any IP or a domain's mail servers, check it points back (FCrDNS) and fix what hurts deliverability." url: "https://prosyo.com/nl/tools/reverse-dns-lookup/" image: "https://prosyo.com/wp-content/uploads/2026/10/cropped-Prosyo-Icon-Transparent-1.png" language: "nl" --- Free Tools # Reverse DNS (PTR) Lookup Find the PTR record behind an IP address or a domain’s mail servers, and check that it points back (forward-confirmed reverse DNS). Reverse DNS (PTR) LookupInstant · results in seconds 100% free 1. 1Fill in 2. 2Run the check 3. 3Fix & use What you get - A plain-English verdict in seconds - Every record found, with what it means - The exact fix for anything that fails **Agent Penny***Your AI SDR* **Do this for every prospect, automatically** Penny finds your buyers, writes personal LinkedIn and email outreach, sends it from your own accounts and drafts every reply. [Start free, 7 days](https://app.prosyo.com/?utm_source=prosyo-tools&utm_medium=tool-side&utm_campaign=reverse-dns-lookup) No card required · Cancel in two clicks **Run outbound on autopilot**Personal LinkedIn and email outreach, sent from your accounts, replies drafted for you.[Start free, 7 days](https://app.prosyo.com/?utm_source=prosyo-tools&utm_medium=article&utm_campaign=reverse-dns-lookup)No card required ## What is a reverse DNS lookup? A reverse DNS lookup finds the hostname behind an IP address. Normal (forward) DNS turns a name like `mail.yourcompany.com` into an IP address; reverse DNS goes the other way, using a PTR (pointer) record published in a special zone, `in-addr.arpa` for IPv4 and `ip6.arpa` for IPv6. For email, reverse DNS is one of the first things a receiving server checks when a connection arrives: a mail server with no PTR record, or one whose name does not point back to the same IP, looks like a compromised home computer or a throwaway server. This free reverse DNS lookup tool finds the PTR record for any IPv4 or IPv6 address. Enter a domain instead and it finds the domain’s mail servers, looks up every one of their IP addresses, and checks forward-confirmed reverse DNS (FCrDNS): whether each PTR hostname resolves back to the same IP. It flags missing records, names that do not point back and generic hostnames that spam filters distrust, and tells you who needs to fix them. ## Key takeaways - Every IP that sends email should have a PTR record. - The PTR hostname should resolve back to the same IP (forward-confirmed reverse DNS). - Use a descriptive hostname such as `mail.yourcompany.com`, not one that contains the IP. - Only the owner of the IP range can set its PTR record: your host, cloud provider or ISP. - On Google Workspace or Microsoft 365, reverse DNS is already handled for you. ## How to use the reverse DNS lookup 1. **Enter an IP address** (for example `8.8.8.8` or an IPv6 address) or **a domain**. 2. **Press “Look up reverse DNS”.** For a domain, the tool finds its MX servers and checks each of their IPs. 3. **Read the table:** each IP, its PTR hostname, whether it points back, and which mail server it belongs to. 4. **Follow the fixes** for anything marked missing or not forward-confirmed. **Free tools fix one email. Prosyo fixes the pipeline.**Penny researches every buyer, writes personal LinkedIn and email outreach and books the meetings, from your own accounts. [Try Prosyo free](https://app.prosyo.com/?utm_source=prosyo-tools&utm_medium=article&utm_campaign=reverse-dns-lookup) ## How reverse DNS works To look up `203.0.113.25`, a resolver reverses the numbers and asks for the PTR record at `25.113.0.203.in-addr.arpa`. The answer is a hostname, such as `mail.yourcompany.com`. IPv6 works the same way, one hexadecimal digit at a time under `ip6.arpa`; the tool handles the expansion for you. **Forward-confirmed reverse DNS** adds a second step: look up the A (or AAAA) record of that hostname and confirm it includes the original IP. When both directions agree, the name was set deliberately by someone who controls both the IP and the domain, which is a basic trust signal for receiving mail servers. | Result | What it means | Risk for email | | --- | --- | --- | | PTR present, points back | Set up correctly. | None from reverse DNS. | | PTR present, does not point back | Name and IP disagree. | Some receivers penalise or reject. | | No PTR record | Nothing published for the IP. | Many receivers distrust or reject the connection. | | Generic PTR (contains the IP, “dynamic”, “dsl”) | Looks like a home or pool address. | Spam filters often treat it as suspicious. | ## Who sets the PTR record? This is the part that surprises people: you cannot set a PTR record in your domain’s DNS. The reverse zone belongs to whoever owns the IP address range. - **Google Workspace, Microsoft 365, Zoho and other mailbox providers:** they own the sending IPs and already publish correct reverse DNS. Nothing for you to do. - **Cloud servers (AWS, Google Cloud, Azure, DigitalOcean, Hetzner and others):** set reverse DNS in the provider’s console or request it from support, usually per IP. - **Dedicated servers and hosting:** ask your hosting provider. - **Office connections:** ask your ISP. Many residential connections cannot have custom PTR records, which is one reason you should not send email directly from them. - **Email sending services (SendGrid, Amazon SES, Mailgun):** shared IPs come with reverse DNS; dedicated IPs can usually have a custom name set in the service’s settings. ## Setting up reverse DNS correctly 1. **Pick a hostname** for the sending server, for example `mail.yourcompany.com`. 2. **Create an A record** (and AAAA for IPv6) for that hostname pointing to the server’s IP, in your own DNS. 3. **Ask the IP owner to set the PTR** for the IP to that same hostname. 4. **Make the server greet with the same name.** Mail servers announce a name in their HELO/EHLO greeting; it should match the PTR. 5. **Check again here** until the tool shows the PTR present and pointing back. ## Reverse DNS and deliverability Reverse DNS is a gate, not a guarantee. Without it, many receivers will not accept your mail at all, and Gmail’s sender guidelines ask all senders to have valid forward and reverse DNS for their sending IPs. With it, you have cleared one basic check; inbox placement still depends on authentication (SPF, DKIM, DMARC), sender reputation, list quality and content. For most teams sending cold email from Google Workspace or Microsoft 365, reverse DNS is never the problem, because those providers manage it. It matters when you run your own mail server, send from an application server, or use a dedicated IP on a sending platform. ## Reverse DNS lookups for security and research Beyond email, reverse DNS helps identify the owner or purpose of an IP address in logs, firewall alerts and analytics: a PTR such as `crawl-66-249-66-1.googlebot.com` suggests a search crawler, which you can confirm with the forward check, since anyone can claim a name in their own reverse zone but cannot make Google’s DNS point back to their IP. ## Worked example A company runs a contact-form mailer on a cloud server at `203.0.113.25`, and form notifications keep landing in spam. The lookup shows no PTR record for the IP. The team creates an A record for `notify.yourcompany.com` pointing to the server, sets the server’s reverse DNS to the same name in the cloud console, adds the IP to SPF with the [SPF Generator](https://prosyo.com/tools/spf-generator/), and checks again: PTR present, forward-confirmed. Combined with DKIM signing, the notifications move back to the inbox. ## Glossary - **PTR record**: the DNS record that maps an IP address to a hostname. - **Reverse zone**: `in-addr.arpa` (IPv4) or `ip6.arpa` (IPv6), managed by the IP owner. - **FCrDNS**: forward-confirmed reverse DNS; the PTR name resolves back to the same IP. - **HELO/EHLO**: the name a mail server announces when it connects. - **Generic PTR**: an automatically assigned name that contains the IP address. ## How Prosyo helps Prosyo sends outreach from your own Google, Microsoft or SMTP mailboxes and your LinkedIn account, inside safe daily limits, so you benefit from your provider’s infrastructure and reputation. It finds verified contacts, writes personal first lines and drafts every reply. [Start a 7-day free trial](https://prosyo.com/pricing/), no card required. ## Related free tools These tools are often used together with the Reverse DNS Lookup. All of them are free and run in your browser. - [MX Lookup](https://prosyo.com/tools/mx-lookup/): See which mail servers receive email for any domain, with their IPs and provider. - [Blacklist Checker](https://prosyo.com/tools/blacklist-checker/): Check a domain or IP against widely used DNS blocklists. - [DNS Lookup](https://prosyo.com/tools/dns-lookup/): Query A, AAAA, CNAME, MX, TXT, NS, SOA and CAA records. - [Domain Health Checker](https://prosyo.com/tools/domain-health-checker/): Score your whole sending setup in one click. ## Frequently asked questions ### What is a PTR record? A DNS record that maps an IP address back to a hostname. It is published in the reverse zone owned by whoever controls the IP address. ### How do I do a reverse DNS lookup? Enter the IP address in the tool above. It returns the PTR hostname and checks whether that hostname points back to the same IP. ### Why does reverse DNS matter for email? Receiving servers use it as a basic trust check. Mail from an IP with no PTR record, or a name that does not point back, is often filtered or rejected. ### How do I set up a PTR record? Ask the owner of the IP address, such as your cloud provider, host or ISP, to set it. You cannot add it in your own domain’s DNS. ### Do I need reverse DNS with Google Workspace or Microsoft 365? No. Their sending servers already have correct reverse DNS. You only manage it for servers or dedicated IPs you control. ### What is forward-confirmed reverse DNS? When the PTR hostname for an IP resolves back to that same IP. It shows the name was set deliberately by someone who controls both. ### Does it work with IPv6? Yes. Enter an IPv6 address and the tool builds the ip6.arpa name and checks it the same way. ## Ready to Accelerate Your Growth? Launch smarter campaigns, convert more leads, and scale your business with ease — all in one place. [Get Started Now](https://prosyo.com/nl/) [Book a Demo](https://prosyo.com/nl/pricing/)