Think of rDNS this way: You sent a beautiful handwritten note to a bank. You wrote the address on the envelope but forgot to mention the return address. What will happen?
The bank will get your letter and read it, but even after receiving the letter, they will treat your letter with suspicion. Why? Because you did not mention your return address, and thus, they Don’t exactly know, who have sent this letter to them
That’s exactly what happens with rDNS. It is just like your return address on the internet. Therefore, when you send mail without proper rDNS configuration, your mail might be treated as suspicious and directly moved to the spam folder.
If you are hosting an email server and sending a large number of newsletters, you will agree that it’s a big challenge to keep your emails secure and trusted so that they go directly to the user’s inbox and not in the spam folder.
That is where rDNS comes in.
So, let us guide you in this blog on how you can configure reverse DNS in your VPS hosting and make your server trusted, secured, and legitimate.
What is DNS and rDNS
When you type a domain name or website URL into your computer, it is converted into an IP address that can be understood only by computers.
In contrast, an rDNS, as the name suggests, reverses the process: it converts the IP address to a human-readable domain name. As a result, rDNS simply reverses the process, converting IP addresses into domain names, while DNS converts domain names to IP addresses.
Why you need rDNS for your VPS Server
But why do we even need to reverse the IP address into a domain name, and why do we exactly use this system? Here is your answer:
It Acts as a Network Trust:
When you have rDNS configured on your VPS, it works as a trusted server hosting. FCrDNS, which stands for matching forward (A/AAAA) (don’t worry, below we will explain this in more detail), is a sign that you control your domain and IP address completely.
Email delivery has better chances with rDNS:
Many email service providers use the rDNS feature to ensure that emails are coming from a legitimate source. Based on rDNS authentication, they decide whether to put a certain email into a receiver’s inbox or spam folder or even push back the message if needed.
Easy-to-read logs with rDNS:
Imagine having hundreds of IP addresses in your log and traffic analysis. Even while you have all the IP addresses in front of your screen, you won’t be able to get any details unless you have rDNS.
Some services require it:
Forget about security and other things, but if you don’t have rDNS configured, certain hosting services will not work at all. They mandate having an rDNS configuration, and without it, their system detects your domain as suspicious and shows failed security checks.
Before we begin: Here’s what you need to be familiar with
Let us first understand some basic yet crucial terminology before we start the step-by-step rDNS configuration process. So, that when we step into the process, you don’t confuse what we are exactly talking about:
- A record:
It is a record of complete IP addresses for their domains to map a hostname. It is mainly used for IPv4 addresses. So for example, when you search mydomain.com. This information first goes to an A record, where this domain is set with a specific IP address, and then you finally access your searched website.
- AAAA record:
An AAAA record is the same as an A record; the only difference is that an AAAA record is used for IPv6, the most recent IP address protocol with a large number of addresses, while an A record is used for IPv4, which is older and obsolete.
- PTR record:
A PTR record associates an IP address with a host name; it is the opposite of an A/AAAA record. As a result, an IP address’s legitimacy is verified through the process of mapping it to a domain name. Thus, we can also say that an A or AAAA record is a tool used in DNS, while a PTR record is used in the rDNS process.
- FCrDNS: :
The combined process of A/AAAA and PTR records is known as FCrDNS. Which means it includes both forward DNS lookup and reverse DNS lookup for the verification of the authenticity of the IP address and domain hosting. “Forward confirmed reverse DNS” is what it literally means.
- VPS provider/hosting provider
A VPS or hosting provider is a company from which you buy hosting services like VPS and dedicated servers. They give you space to host your website and application on the internet.
Before we begin: Here’s what you need (prerequisites)
Now that you know the importance of rDNS, you want to configure the rDNS to your hosting but are confused about what the things you require are before you start the process. So, here are some prerequisites:
- A domain name: You need to have a domain name for which you will set up rDNS, like com.
- Domain’s DNS control panel access: This is the place where you will add A/AAAA records for your domain name
- VPS IP address: The VPS provider should have given you the correct IP address that points to your domain.
- VPS control panel: Since the PTR records are mostly managed by VPS providers and you need to make changes to them, you require the VPS control panel access.
Step-by-step guide to configure rDNS in VPS
Here is the step-by-step walkthrough to configure your rDNS in VPS. To make the process easier, we will take some presumed domain name and IP address examples.
Domain Name (Example): Prospos.com
VPS IP Address example: 203.0.113.45
Step 1: Get the hostname you want:
Selecting the appropriate hostname for your VPS hosting is the first step to configure rDNS. The hostname associated with your IP address will be displayed in the PTR record. It is necessary to stick with your hostname, as if you later change the hostname but forget to update PTR, it will result in a mismatch and unfetched rDNS.
Step 2: Create a forward DNS record (A/AAAA) for the hostname:
To guarantee that your hostname resolves back to the same IP address, a forward DNS record is essential. It is used for FCrDNS and to increase trust.
To create the A/AAAA record, first you need to go to the DNS manager where your domain is hosted (your domain registrar) and add the following:
- Type There are two types of forward DNS records and you need to choose according to your IP address: “AAAA” for IPv6 addresses and “A” for IPv4 addresses.
- Name: mail or mx1 or smtp. If you choose mail, it will create prospos.com; similarly, if you choose mx1 or smtp, it will create mx1.prospos.com or smtp.prospos.com, respectively.
- Value: 203.0.113.45. Which means here you need to write your VPS IP address for which you are configuring rDNS
- TTL: By default it is set as 1 hour; you can leave it as it is.
Step 3: Set the PTR for your hosting:
This is one of the most crucial steps for rDNS configuration. It helps look up rDNS from IP address to hostname. PTR can be set up for your hosting in two different ways.
● Option A – Provider control panel (self-service)
If your server provider gives you the option to manage reverse DNS or PTR through the control panel, you can use this feature to set the pointer record. Just find the edit option for the rDNS/PTR/IP management and enter your A/AAAA record name like mail.prospos.com.
● Option B – Through the support ticket
But if your hosting provider does not provide the PTR editing option, you can raise a ticket and their team will set the PTR for you. Since they own the complete PTR record, they can set it reliably for your server hosting.
Step 4: Wait for propagation:
Your hosting is almost configured for rDNS; you now just need to wait so that it can start appearing everywhere. Usually it takes from a few minutes to 1 or 2 days. But that is mainly because DNS uses cached information.
Step 5: Verify both forward and reverse lookups:
Once the setup and wait are over, we need to check if it is configured well and if both forward and reverse DNS are working fine. To check this, you can use commands from any computer (Linux/macOS terminal or Windows).
To check the reverse lookup (IP address to hostname), give the following command:
Linux/macOS (dig)
Dig +short -x 203.0.113.45
Or
Host 203.0.113.45
Windows (nslookup)
nslookup 203.0.113.45
After giving the command, you should get the result of your hostname, like mail.prospos.com. But if it shows the wrong hostname or shows nothing, it indicates that PTR is not configured yet. You might need to recheck every step carefully.
To check the forward lookup (hostname to IP address), the following commands can be used:
Dig + short mail.propos.com
Nslookup mail.prospos.com
The expected result should be your IP address and if you don’t get the IP address result, it again suggests some error in configuration.
Step 6: Additional settings for email servers:
If you are setting up rDNS for email servers, you need to ensure the mail’s default greetings match the PTR. Many email servers introduce themselves using the default name when sending emails, like “HELO/EHLO.” Configure your mail software to use the same name as your hostname set in the PTR; otherwise, your mail might be treated as suspicious.
Step 7: For IPv6, there’s more for rDNS
In case you have an IPv6 address for your hosting, the process of rDNS configuration looks scarier, as it uses the ip6.arpa format and requires reversing hexadecimal digits of the address. However, your server providers usually manage it and they can understand better and help you set the PTR easily. So, for IPv6, it is better to raise a ticket and set your PTR through your hosting provider’s technical team for a seamless process.
Troubleshooting for common problems
In the process of configuring your server for rDNS, forward and reverse lookup, you may encounter some common yet frustrating issues. To troubleshoot these problems, you can work on the following:
PTR shows a different hostname: Contact the provider and ask to change it to your desired hostname and ensure A record points correctly
PTR exists but forward does not match: An A/AAAA record might have some error and to fix this, you have to ensure it is set right and points to the same IP address
Provider refuses or won’t set PTR: If your server provider refuses to set PTR for your hosting, you can’t do much about it except change the hosting provider entirely.
Email still goes to spam: If your email still goes to spam, that suggests it is not the rDNS issue but another problem like SPF, DKIM, and DMARC email authentication. You can also ensure by asking your server provider if your IP is on spam blacklists or something similar.
Conclusion
In conclusion, configuring rDNS is a small step but provides big benefits, from a clearer server identity and better email delivery to fewer headaches and smooth system log checks. You can easily configure rDNS in your hosting by setting an A/AAAA record, a PTR record, and an FCrDNS checkup. We have shared with you a step-by-step proc process and if you need any additional services, contact us now to get help.
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