rDNS stands for reverse DNS: looking up the hostname that belongs to an IP address, the opposite of the usual name-to-address lookup. It is stored in a PTR record, and mail servers use it to check who is behind a sending address.

How do I check the rDNS of an IP address?

On Linux or macOS run dig -x followed by the IP address, or host followed by the IP. On Windows run nslookup followed by the IP, or Resolve-DnsName with -Type PTR in PowerShell. To confirm it properly, look the returned hostname up again and check it gives back the same IP.

Is rDNS the same as a PTR record?

Effectively yes. "rDNS" names the concept of resolving an IP address to a hostname; "PTR record" names the DNS record type that implements it.

Why does rDNS matter for email?

Many receiving mail servers check that a sending IP has a PTR record, and that the hostname it gives resolves back to the same address. An IP with no PTR, or one pointing at a generic provider hostname, looks less accountable and is treated with more suspicion.

Can I set my own PTR record?

Not directly. Reverse DNS lives in the zone belonging to whoever owns the IP block, so you ask your hosting provider and they set it. Only forward DNS is under your control.

Do I need a dedicated IP for custom rDNS?

Yes. A PTR record applies to the whole address, so on an IP shared between customers it would be meaningless. Every plan here includes a dedicated IPv4 address.

Can I have a different PTR for each of my domains?

Not on one IP address. A PTR belongs to an address, not a domain, so one server gets one reverse hostname. If you need several, you need several IP addresses.

Is rDNS enough for good deliverability on its own?

No. It removes one reason to distrust you rather than creating trust. SPF, DKIM, DMARC, a gradual volume ramp and a clean opt-in list all matter alongside it.

Forward-Confirmed reverse DNS: the receiving server resolves your IP to a hostname via the PTR record, then resolves that hostname back to an IP, and checks the two match. Passing it is a basic sign of a properly configured mail server.

Is rDNS used for anything besides email?

Yes. Google documents reverse DNS as the way to verify that a visitor claiming to be Googlebot really is: look up the PTR of the IP, check it is a Google domain, then look that name up forward and confirm it returns the same IP. Logs and network tools also show rDNS names, which makes them easier to read. It plays no part in how websites rank.

How do I get rDNS set on a VPS For Life server?

Create an A record for the hostname you want, pointing at your server's IP, in your own domain's DNS. Then open a ticket with the IP address and the exact hostname. We check the A record first, because a PTR without it fails the forward check, and then our network team sets the PTR. It is free on every plan, for IPv4 and IPv6.

Is Port 25 guaranteed on every plan, or just open?

Both, depending on the range, and the difference is worth knowing before you buy. Outbound Port 25 is open by default on all 16 plans — no ticket, no approval step. On NVMe VPS, Cloud VPS, Classic VPS and VDS it is written into the published plan specification. On it is open because of how the network is run rather than as a documented guarantee. In practice it behaves the same on all of them, but if your business stops when you cannot send, buy the range that puts it in writing.

Definition · Reverse DNS

What is rDNS?

Reverse DNS turns an IP address back into a hostname. Mail servers check it to see whether the machine sending them a message is who it claims to be — which is why an IP with no PTR record, or a generic one, is treated with suspicion.

In More Detail rDNS VPS

Lookups a receiving server makes

IP → hostname, then hostname → IP. Both must agree.

PTR record: the IP’s claimed name
A record: does that name point back?
HELO name matching both
You cannot set the PTR yourself

What is rDNS? The definition.

Reverse DNS, or rDNS, maps an IP address back to a hostname — the opposite direction to an ordinary DNS lookup, and it is stored in a record type called PTR. Forward DNS answers “what address does mail.example.com point to?”; reverse DNS answers “what name does 203.0.113.10 claim?”. Mail servers use it as a cheap identity check: they look up the PTR for the connecting address, then look that hostname up again and confirm it resolves back to the same IP. That round trip is called Forward-Confirmed reverse DNS, and passing it is one of the oldest signals that a sending machine is run by somebody taking responsibility for it.

rDNS and PTR are the same thing — rDNS is the concept, PTR the record type.
Direction: IP address → hostname, the reverse of a normal lookup.
FCrDNS: the check that the hostname resolves back to the same IP.
Who sets it: the owner of the IP block, which is your hosting provider.
One per IP address — not one per sending domain.
Needs a dedicated IP to be meaningful at all.

In More Detail

Why it cannot be faked

Your mail server introduces itself with a HELO greeting, and it can say whatever it likes — there is nothing stopping a spam machine claiming to be mail.yourbank.com. The PTR record is different: it lives in the DNS zone belonging to whoever owns the IP address block, so only that party can set it.

So when the greeting and the PTR agree, and the hostname resolves back to the same address, the receiving server learns something real: whoever controls that IP space vouched for the name. It is a weak signal on its own, and it is cheap to check, which is why practically everyone checks it.

Why you have to ask your provider

You control forward DNS for your own domain, so you can create mail.example.com pointing at your server whenever you like. Reverse DNS lives in a different zone — one derived from the IP address and delegated to whoever owns that address block.

That is your hosting provider. This is why every host sets PTR records on request rather than giving you a field in a control panel, and why a provider that will not do it is a genuine blocker for anyone sending mail.

One record per address, not per domain

A PTR record belongs to an IP, so a single server has one reverse hostname no matter how many domains it sends for. People sending for several brands from one machine ask about this constantly, and the answer disappoints them.

The usual approach is to pick one neutral hostname on your own infrastructure domain for the PTR and the HELO greeting, and let SPF, DKIM and DMARC carry the per-domain authentication. If you genuinely need separate reverse names, you need separate IP addresses.

How to Check the rDNS of an IP Address

One command shows the PTR record. A second confirms it, the same way a receiving mail server does. Prefer a browser? Use our free PTR / rDNS lookup tool.

Linux or macOS — the PTR for an address, then the forward lookup of the name it returns:

dig -x 203.0.113.10 +short
dig mail.example.com +short

host 203.0.113.10 gives the same answer in one line.

Windows — either of these:

nslookup 203.0.113.10
Resolve-DnsName 203.0.113.10 -Type PTR

Where the record actually lives. A reverse lookup is a normal DNS query for a special name. The address is written backwards under in-addr.arpa, so the PTR for 203.0.113.10 is stored at 10.113.0.203.in-addr.arpa. IPv6 works the same way under ip6.arpa, one hexadecimal digit at a time. Those zones belong to whoever holds the address block, which is why your hosting provider sets the record and you do not.

What different PTR results look like to a receiving mail server
What the lookup returns	Example	How mail filters tend to read it
Nothing	No PTR record	Often rejected or heavily penalised
A generic provider name	`203-0-113-10.static.example.net`	Looks unmanaged. Many filters score it down
Your hostname, but its A record points elsewhere	`mail.example.com` → a different IP	Fails the forward check
Your hostname, matching its A record and HELO	`mail.example.com` ↔ `203.0.113.10`	What a properly run mail server looks like

Getting rDNS Set on a VPS For Life Server

Free on every plan, for IPv4 and IPv6. Three steps, and the first one is yours.

1
Create the A record

In your own domain’s DNS, point the hostname you want, for example mail.yourdomain.com, at your server’s IP. A PTR without it fails the forward check, so we look for it first.
2
Open a ticket

Send the IP address and the exact hostname. Once the A record checks out, our network team sets the PTR on our side of the address space.
3
Verify both directions

Run the two lookups above. When dig -x returns your hostname and the hostname returns your IP, you pass FCrDNS. Set your mail server’s HELO name to match.

The full walkthrough, including HELO settings and what to do if a lookup still shows the old name: rDNS VPS.

What Is rDNS? — Questions

On Linux or macOS run dig -x 203.0.113.10 +short or host 203.0.113.10; on Windows, nslookup 203.0.113.10 or Resolve-DnsName 203.0.113.10 -Type PTR. Then look the returned hostname up again and check it gives back the same IP. Or use our free PTR / rDNS lookup tool.

Port 25 open, dedicated IPv4, rDNS on request.

From $4.95 a month with root access from the first second — plus a 7-day money-back guarantee.

See All 16 Plans Ask Before You Order