How to Set Up Reverse DNS for Email Servers

Without reverse DNS (rDNS), your emails could be flagged as spam or rejected by major providers like Gmail and Yahoo. Setting up rDNS ensures your email server's IP address is linked to your domain, proving your emails come from a legitimate source. Here’s the quick process:

1. Understand rDNS and PTR Records: rDNS resolves an IP address back to a domain using PTR records. For example, the IP 192.168.1.100 maps to 100.1.168.192.in-addr.arpa.
2. Why It Matters: Major email providers now require proper rDNS setup for email authentication. Missing or incorrect PTR records can block your emails.
3. Requirements:
   • Access to DNS management.
   • A dedicated IP address (shared IPs won't work).
   • Proper hostname and A record setup.
4. Steps to Configure rDNS:
   • Find your server’s public IP.
   • Request a PTR record through your hosting provider.
   • Test your setup using tools like nslookup or MXToolbox.
5. Additional Tips:
   • Ensure Forward-Confirmed rDNS (FCrDNS): Your domain’s A record and PTR record must match.
   • Implement SPF, DKIM, and DMARC for stronger email authentication.

Shortcut: Tools like Infraforge automate the entire process, saving time and improving deliverability.

Proper rDNS is critical for avoiding spam filters and ensuring your emails reach inboxes. Ready to dive in? Let’s set it up!

What is Reverse DNS and PTR Records

Reverse DNS Basics

Reverse DNS (rDNS) operates as the flip side of regular DNS lookups. While forward DNS converts domain names into IP addresses, rDNS does the opposite - it resolves an IP address back to a domain name.

This functionality is especially important for email servers during message delivery. When your server sends an email, the receiving server conducts a reverse DNS lookup on your IP address to confirm it matches the domain you claim to represent. This verification helps separate legitimate servers from potentially malicious ones. Let’s dive into how PTR records make this process possible.

PTR Records Explained

PTR (Pointer) records are the backbone of reverse lookups. They map an IP address to a domain name, essentially performing the reverse function of an A record. While A records link domain names to IP addresses, PTR records connect IP addresses back to domain names.

The structure of PTR records follows a specific format. For IPv4 addresses, PTR records use the .in-addr.arpa domain, while IPv6 addresses rely on .ip6.arpa. For example, if your email server’s IP address is 192.168.1.100, the corresponding PTR record would appear as 100.1.168.192.in-addr.arpa (notice the reversed order of the IP octets). These records not only enable reverse lookups but also serve as a safeguard, filtering out suspicious sources. By adding an extra layer of verification, they work alongside other email authentication methods to confirm a server’s authenticity. This is why PTR records are so critical for email operations.

Why Email Servers Need rDNS

Reverse DNS is a cornerstone for email servers in their fight against spam and in verifying sender authenticity. With stricter authentication protocols now in place, PTR records have become essential for email delivery. When an email server receives a message, it uses reverse DNS to distinguish legitimate senders from compromised servers that might be used for spamming. Spammers often fail to set up proper reverse DNS records, making it easier to identify and block their attempts.

Starting February 1, 2024, Google and Yahoo began enforcing tighter email authentication standards, which include proper PTR record configuration. Email-sending systems are now required to pass Forward-Confirmed reverse DNS (FCrDNS) checks, making accurate rDNS setup more important than ever.

Some SMTP servers take these checks even further by rejecting emails if the rDNS doesn’t align with the HELO command. The HELO command identifies your domain name during the email-sending process, and any mismatch between the domain and the IP address can result in automatic rejection. This means that missing or incorrect PTR records don’t just affect spam filtering - they can lead to outright rejection of emails from servers without proper rDNS configuration. Even legitimate emails may fail to reach their recipients if the server isn’t set up correctly.

That said, while rDNS is a critical piece of the puzzle, it’s not the only factor determining email deliverability. Mailbox providers also evaluate the overall reputation of your IP address and domain when deciding how to handle your emails. However, PTR records remain a key requirement for maintaining clean email practices and ensuring your messages land where they’re supposed to.

Requirements Before Setup

Before diving into reverse DNS configuration, it's essential to ensure you meet certain prerequisites. Skipping any of these steps could lead to authentication issues.

DNS Management Access

The first and most important requirement is having access to manage your DNS records. This means you’ll need control over an authoritative nameserver or your DNS management system to create or modify PTR records. The level of access you need depends on your hosting setup.

If you’re using an email service provider (ESP) like Google Workspace or Microsoft 365, they typically handle reverse DNS (rDNS) configuration for their shared IP addresses automatically. However, if you’re running your own mail server or have a dedicated IP address provided by your ESP, the responsibility for rDNS setup falls on you.

For organizations with direct IP assignments, DNS management is usually straightforward. But if your IP is assigned by an internet service provider (ISP), you may need their assistance to manage PTR records. Some hosting providers also restrict direct edits to PTR records, which may require you to submit a support ticket to request changes. In such cases, you’ll need to ask your hosting provider or ESP to create a PTR record that resolves your IP address to your domain.

Dedicated IP Address

A dedicated IP address is another key requirement. Reverse DNS can only resolve one hostname per IP address, which makes dedicated IPs essential for custom email server configurations. Shared IPs, often used by multiple senders, cannot support unique rDNS records, making them unsuitable for this purpose.

Beyond technical compatibility, dedicated IPs offer clear benefits for email deliverability. They allow you to build a stronger sending reputation and avoid being affected by the behavior of other senders on shared IPs. A dedicated IP ensures that your DNS records align with your company’s domain, which helps establish trust with ISPs.

This setup also gives you full control over your sending reputation, meaning your email deliverability depends entirely on your organization’s practices, not on shared IP users. To confirm whether you have a dedicated IP, you can use tools like IP WHOIS Lookup to check the ownership of your IP block.

Hostname and A Record Setup

Before creating a PTR record, it’s critical to confirm that your hostname and A record are properly configured. This alignment is the foundation of Forward-Confirmed reverse DNS (FCrDNS), a standard required by major email providers.

Start by ensuring the A record for your hostname points to the correct IP address of your mail server. For example, if your mail server’s hostname is mail.yourcompany.com, the A record should resolve to your server’s IP address. Use diagnostic tools to verify this setup.

Consistency across your email server configurations is crucial. The hostname used in your SMTP banner, HELO/EHLO greeting, and PTR record must match. Any discrepancies can lead to authentication failures or trigger spam filters.

To check if a PTR record already exists for your IP address, use online tools like DNSLookup.io, PTRRecord.com, ViewDNS.info, or MXToolbox. If the PTR record is incorrect, you’ll need to update it. If no record exists, you’ll need to create one.

After making changes to your A record, allow time for DNS propagation before proceeding with rDNS setup. DNS updates can take anywhere from a few minutes to 48 hours to propagate globally, though most changes are visible within a few hours.

To verify your current configuration, tools like centralops.net’s Domain Dossier can confirm whether the hostname returned in SMTP results matches your intended mail server hostname.

Once you’ve met these prerequisites, you’re ready to begin configuring reverse DNS.

How to Configure Reverse DNS

To set up reverse DNS (rDNS) for your email server, you’ll need to follow a straightforward process. There are three main steps: identifying your server’s public IP address, creating a PTR record, and testing the configuration to ensure everything works as intended.

Find Your Server's Public IP

Start by pinpointing your email server’s public IP address. The easiest way? Reach out to your hosting provider - they can provide you with the IP address assigned to your mail server. If you’d rather handle it yourself, log into your domain's DNS admin panel and check the "A" records for hostnames like mail.yourdomain.com or imap.yourdomain.com.

Alternatively, you can use command-line tools. For instance, run ping mail.yourdomain.com or nslookup mail.yourdomain.com on your Windows or Mac system, and it’ll reveal the IP address.

One thing to watch for: if you’re using a third-party spam filtering service, the MX query results might show the filtering provider’s IP address instead of your actual email server’s public IP. Double-check this to avoid confusion.

Create the PTR Record

Once you have your public IP, the next step is creating a PTR record. PTR records work within reverse DNS zones, which are different from standard DNS zones. For IPv4 addresses, these records are added under the in-addr.arpa domain, while IPv6 addresses use the ip6.arpa domain.

In most cases, you’ll need to contact your hosting provider or the organization managing your IP block to create the PTR record. They control the reverse DNS zones and can handle this for you. When making your request, supply the following:

• Your server’s public IP address.
• The fully qualified domain name (FQDN) you want the IP to resolve to. Be specific - use the full domain (e.g., mail.yourcompany.com) rather than a partial name like "mail".

For IPv4 addresses, the IP address octets must be reversed before adding the PTR record, as explained in earlier sections.

"A PTR record can be added only in the reverse DNS zone (RDNS) and not in a regular domain zone." - Gcore Docs

Once the PTR record is created, allow up to 24 hours for DNS propagation.

Test Your rDNS Setup

After the PTR record has been created and propagated, it’s time to test your configuration. Use command-line tools like nslookup <your_IP> to check that the IP resolves to your hostname. You can also use online tools such as MXToolbox to verify the setup. For proper Forward-Confirmed reverse DNS (FCrDNS) compliance, ensure that the IP resolves to the hostname and the hostname resolves back to the IP.

To further validate your setup, send test emails to major providers like Gmail, Outlook, and Yahoo. Monitor the deliverability results. If you run into issues, double-check that your PTR record matches your SMTP banner hostname and HELO/EHLO greeting exactly.

Once you’ve confirmed the rDNS configuration is working correctly, you’re ready to move on and implement additional email authentication methods in the next steps.

Email Authentication Best Practices

Reverse DNS (rDNS) is just the starting point for a thorough email authentication setup. To protect your email server’s reputation and ensure your messages land in inboxes - not spam folders - you need to go beyond basic rDNS configuration. By layering additional authentication protocols on top of rDNS, you can secure every email your server sends.

Set Up Forward-Confirmed Reverse DNS

Forward-Confirmed Reverse DNS (FCrDNS) adds an extra layer of validation by ensuring that your domain’s A record and PTR record are perfectly aligned.

"FCrDNS ensures that both the forward DNS lookup (from domain to IP) and the reverse DNS lookup (from IP to domain) match each other."

The importance of FCrDNS has increased significantly, especially since February 2024, when providers like Google and Yahoo began requiring it. To implement FCrDNS, make sure your domain has a valid DNS A record pointing to your server’s IP address. Then, confirm that the PTR record maps that IP back to the same domain. Regularly check your DNS configuration using online tools, as DNS changes can take up to 24 hours to fully propagate.

Use Additional Authentication Protocols

To strengthen your email authentication, protocols like SPF, DKIM, and DMARC are essential. Here’s how they work:

• SPF (Sender Policy Framework): Confirms that an email is sent from an authorized IP address.
• DKIM (DomainKeys Identified Mail): Ensures that the email content hasn’t been altered during transit.
• DMARC (Domain-based Message Authentication, Reporting, and Conformance): Combines SPF and DKIM results, giving instructions to receiving servers on how to handle messages that fail authentication.

Unfortunately, many senders overlook these protocols, leaving their domains vulnerable to misuse. As Marcel Becker, Senior Director of Product at Yahoo, explains:

"The end goal is ideally a policy of p=reject. That's what DMARC is for. Ensuring that your domain cannot be spoofed and protecting our mutual customers from abuse."

Start with a DMARC policy of p=none to monitor performance without affecting email delivery. Once you’re confident in your configuration, transition to p=quarantine and eventually to p=reject. Moving to a p=reject policy can improve email deliverability by over 10% with major providers like Gmail.

Automate rDNS with Infraforge

Managing email authentication manually can be tedious, especially if you’re handling multiple domains. This is where automation tools like Infraforge come in. Infraforge simplifies the process by automating rDNS, SPF, DKIM, and DMARC configurations, making it easier to scale your email campaigns without technical headaches.

"Ship Faster With Zero Technical Overhead. Get started in just minutes with automated DNS setup for every new domain and pre-configured email authentication (DMARC, SPF, DKIM). Make quick changes with bulk DNS updates across your entire infrastructure." - Infraforge

Companies using Infraforge report significant improvements. For example, properly configured DMARC leads to 90% fewer successful phishing attempts, while DKIM reduces the risk of email tampering by 30%. Infraforge also supports businesses focused on cold email outreach by offering dedicated IPs, pre-warmed domains, and automated DNS management. This allows users to focus on crafting impactful email campaigns instead of dealing with complex technical setups.

"Infraforge improved our email deliverability. What I like about Infraforge is its ease of use and quality of support." - Silver L, CEO

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Infraforge vs Other Solutions

Reverse DNS (rDNS) setup can be handled manually through a VPS or by using traditional DNS hosting services, but both options often lack the scalability and simplicity needed for cold email campaigns. Getting rDNS right is key for strong email authentication, and that's where Infraforge consistently stands out. Let’s see how it measures up against these alternatives.

Infraforge vs Manual VPS Setup

Manually configuring reverse DNS on a VPS is no walk in the park. It demands technical know-how and constant management. You’ll need to set up PTR records, manage DNS propagation, and individually configure email authentication protocols like SPF, DKIM, and DMARC. This process can easily consume hours and requires ongoing attention to ensure everything runs smoothly.

Infraforge eliminates these headaches by automating the entire setup process. What typically takes hours can be done in just minutes with Infraforge.

Feature	Manual VPS	Infraforge
Setup Time	Several hours	5 minutes
DNS Configuration	Manual (SPF, DKIM, DMARC)	Automated
IP Management	Shared or manually configured dedicated IPs	Dedicated IPs included
Reputation Control	Limited, influenced by server history	Full control with private infrastructure
Scaling	Requires individual provisioning	Multi-IP provisioning with API
Cost	Higher due to maintenance overhead	Predictable pricing at $651/month for 200 mailboxes

Now let’s take a look at how Infraforge stacks up against traditional DNS hosting.

Infraforge vs Traditional DNS Hosting

Traditional DNS hosting services are designed for general DNS management, not email-specific infrastructure. While they allow manual configuration of PTR records and authentication protocols, they fall short in areas critical to email deliverability. For instance, dedicated IPs must be purchased separately, domain warming requires manual effort, and reputation monitoring often relies on third-party tools. This fragmented approach can lead to errors and reduced deliverability.

The main drawback of traditional DNS hosting is its lack of integration for email deliverability. Unlike Infraforge, which combines everything into one streamlined solution, traditional services require piecing together multiple tools and services.

Feature	DNS Hosting	Infraforge
DNS Setup	Manual configuration	Automated (SPF, DKIM, DMARC)
IP Addresses	Shared or separate purchase required	Dedicated IPs included
Domain Masking	Not available	SSL proxies with domain masking
Deliverability Focus	General DNS services	Built specifically for cold outreach
Bulk Management	Limited bulk operations	Bulk DNS updates across infrastructure
Support	General technical support	Cold outreach experts
Pricing (10 mailboxes)	$5–15/month + separate IP costs	$17/month (includes everything)

Another key issue with traditional DNS hosting is shared infrastructure. If other users on a shared service engage in poor email practices, your deliverability could take a hit. Infraforge avoids this problem entirely by offering private infrastructure, giving you full control over your sender reputation.

For businesses managing multiple domains, Infraforge’s automation is a game-changer. Bulk DNS updates across your entire infrastructure save time and effort, whereas traditional DNS hosting requires configuring each domain individually.

"Infraforge is the only choice. For those who are okay with inefficiencies, there are plenty of other options. But if you want results, you go with Infraforge. Period!" - Rahul Lakhaney, Former VP, Gartner, now CEO @ Enrich.so and Maximise

Conclusion

Reverse DNS plays a vital role in ensuring email deliverability. Without properly configured PTR records that link your IP addresses to legitimate hostnames, your emails could end up flagged as spam or outright rejected by receiving servers.

Setting it up involves several steps: securing a dedicated IP, gaining access to DNS management, creating PTR records, and ensuring forward-confirmed reverse DNS. For businesses managing their own mail servers, this process can be technically demanding and time-intensive, requiring ongoing upkeep.

Thankfully, automated tools like Infraforge streamline the entire process. These solutions handle DNS configuration, PTR record management, and authentication protocols effortlessly. What might take hours of manual effort can be reduced to just minutes, with added perks like dedicated IPs, pre-warmed domains, and continuous maintenance.

As email authentication standards grow stricter, major ISPs increasingly rely on reverse DNS checks to verify sender legitimacy. Whether you opt for manual configuration or an automated service, having valid PTR records is no longer optional - it’s a must for preserving your sender reputation and ensuring your emails land in inboxes.

When combined with SPF, DKIM, and DMARC, reverse DNS creates a strong backbone for secure and reliable email delivery. Laying this groundwork correctly from the beginning is key to keeping your email infrastructure running smoothly.

FAQs

Why do you need a dedicated IP address to set up reverse DNS for email servers?

A dedicated IP address plays a key role in setting up reverse DNS (rDNS). It connects your IP address directly to your domain name, enabling mailbox providers to confirm the legitimacy of your email server. This verification process helps improve email deliverability by establishing trust with recipient servers and reducing the chances of your emails being marked as spam.

On the other hand, if you're using a shared IP, configuring reverse DNS becomes impossible. Shared IPs are used by multiple domains, making it difficult for providers to link your emails to your specific domain. This can negatively affect your sender reputation and, ultimately, your email performance.

What is Forward-Confirmed reverse DNS (FCrDNS) and how does it improve email deliverability?

What Is Forward-Confirmed Reverse DNS (FCrDNS)?

Forward-Confirmed Reverse DNS (FCrDNS) is a method used to confirm that an IP address is properly associated with a domain name, and that the domain name, in turn, resolves back to the same IP address. This two-way verification process helps build trust between email servers.

When this alignment is in place, it strengthens your sender reputation and lowers the chances of your emails being marked as spam or outright rejected. It plays a crucial role in improving email deliverability by signaling to receiving servers that your email traffic is legitimate and not a result of spoofing.

What advantages does Infraforge offer for email authentication compared to setting up DNS manually?

Infraforge takes the hassle out of setting up critical DNS records like SPF, DKIM, and DMARC. By automating these configurations, it ensures they’re done right and follow established best practices. This not only saves time but also minimizes the chance of mistakes that often come with manual setup.

Beyond automation, Infraforge offers features like dedicated IPs, pre-warmed domains, and multi-IP provisioning. These tools are specifically designed to boost email deliverability and simplify large-scale email operations. For businesses running cold email campaigns or managing high-volume email sending, Infraforge provides a smoother, more dependable alternative to manual DNS management.

Related posts

• DNS Setup for Cold Email: Complete Guide
• SPF, DKIM, DMARC Testing for Cold Email Outreach
• How SPF, DKIM, DMARC Improve Deliverability