Email is a valuable communication channel, especially for many businesses and email marketers. It is known to develop the highest ROI, which should make inbox placement and email deliverability a priority. Â
The capability to ensure that your emails are delivered to the intended recipient is a simple idea, yet there are still some email users in fact a study showed that out of 1000 email users 39% of them rarely or never conduct email list hygiene.
One of the basic, yet crucial aspects in the improvement of the email deliverability process are implementing email authentication protocols, such as the Reverse DNS (rDNS) lookup.Â
rDNS lookup is an instrumental authentication system that helps establish trust between mail servers. Its main function involves verifying the legitimacy of email senders, it is a process that involves the confirmation if an IP address sends an email correctly maps back to a domain name.Â
However, when reverse DNS lookup fails, there are associated consequences that may get involved in your capabilities in using your emails.
Consequences that will result into your emails getting:
- Rejected
- Being flagged as spamÂ
- Suffering from poor email deliverability
Having these can damage your reputation making it more challenging for email marketers and other businesses to interact and reach their audiences effectively.
Explaining Reverse DNS (rDNS) Lookup
Reverse DNS (rDNS) lookup is the process of resolving an IP address to a domain name. This is the opposite of the standard DNS lookup, which maps a domain name to an IP address.
How Reverse DNS Works
It all starts when an email is sent. The recipient’s mail server will conduct an rDNS lookup verifying the address of the sending server. Once the IP address correctly resolves to a valid domain, the email will have a higher chance of getting accepted. However, when the lookup fails or returns no result, the email is more than likely to be marked as spam or get rejected.Â
rDNS and PTR Records
- PTR (Pointer) records are used to define rDNS.
- Every mail server IP should have a PTR record mapping it to a valid hostname.
- If no PTR record exists or is misconfigured, the recipient’s server cannot verify the sender, leading to failed rDNS checks.
Why Do Reverse DNS Lookup Failures Occur?
There are tons of reasons why an rDNS lookup failure occurs. Each of them stems from failure to set up a proper authentication process that can lead to email delivery failure, which gravely affects your email reputation.Â
Missing PTR Record
If an IP address lacks a PTR record, the recipient’s mail server cannot perform an rDNS lookup, leading to automatic email rejection or spam filtering.
Incorrect rDNS Configuration
If the PTR record does not match the sending domain, mail servers will not recognize the sender as legitimate, impacting email delivery.
Dynamic or Blacklisted IP Addresses
- Emails sent from dynamic IP addresses (e.g., home networks, ISPs) often fail rDNS checks.
- IPs on blacklists will experience rDNS failures, reducing deliverability.
Mismatched Forward and Reverse DNS
For proper rDNS validation:
- The forward DNS (A record) must match the reverse DNS (PTR record).
- If the A record and PTR record do not align, rDNS lookup will fail.
ISP or Hosting Provider Restrictions
Some Internet Service Providers (ISPs) do not allow custom rDNS configurations, making it impossible to set a valid PTR record.
Reverse DNS Failures Impact on Email Deliverability
The following are some of the repercussions that an email user can acquire when there is an rDNS lookup failure. It involves the potential consequences you can acquire especially for your email deliverability.Â
Higher Spam Score and Email Rejections
Major email providers like Google, Microsoft, and Yahoo use rDNS verification to filter out spam and fraudulent senders. When an rDNS lookup fails:
- Emails are more likely to be marked as spam.
- Messages may be rejected outright.
Damaged Sender Reputation
If emails regularly fail rDNS checks, the sender’s domain reputation and IP trustworthiness decline, leading to poor deliverability in the long term.
Poor Open and Engagement Rates
When emails land in the spam folder, recipients are unlikely to see or engage with them, reducing overall marketing effectiveness.
Increased Bounce Rates
Some mail servers are configured to reject all emails that fail rDNS lookup, leading to higher bounce rates and hindered communication efforts.
How to Properly Configure Reverse DNS and Prevent Failures
When rDNS fails, emails are more likely to be blocked, flagged as spam, or undelivered. This, of course, can result in damaging the sender’s reputation and may affect their communication efficiency.
Step 1: Set Up a PTR Record
To ensure successful rDNS lookups:
- Request your hosting provider or ISP to create a PTR record for your mail server’s IP.
- The PTR record should point to the fully qualified domain name (FQDN).
Example PTR record setup:
123.45.67.89.in-addr.arpa. IN PTR mail.yourdomain.com.
Step 2: Ensure Forward and Reverse DNS Match
- The A record (forward DNS) should resolve your domain to an IP.
- The PTR record (reverse DNS) should resolve the IP back to the domain.
- Use nslookup or dig commands to verify proper configuration.
Step 3: Use a Dedicated IP for Email Sending
- Avoid dynamic IPs by using a static IP address for outbound emails.
- Dedicated IPs allow better reputation management and deliverability tracking.
Step 4: Verify Your Configuration with rDNS Lookup Tools
Use online tools to confirm rDNS setup:
- MXToolBox – Checks PTR records and rDNS health.
- Google Admin Toolbox – Tests mail server authentication.
- Nslookup/Dig Commands – Verifies domain-to-IP and IP-to-domain mapping.
Step 5: Monitor Blacklists and ISP Restrictions
- Check if your IP is listed on Spamhaus, Barracuda, or UCEPROTECT.
- Work with your ISP to resolve any listing issues.
Step 6: Implement SPF, DKIM, and DMARC
- SPF (Sender Policy Framework): Validates permitted sending IPs.
- DKIM (DomainKeys Identified Mail): Ensures email integrity.
- DMARC (Domain-based Message Authentication): Protects against spoofing and phishing.
Step 7: Warm Up Your Email Reputation with WarmyÂ
Warmy.io is known for its free email deliverability test. It is a critical process that helps you assess the performance of your email and provide you with the information to enhance your email deliverability and reputation.
It also provides free SPF Record Generator that can help specify which mail servers have the authority to send emails for a specific domain, and DMARC Record Generator to avoid email spoofing and phishing by enabling domain owners to provide the specifications of how their emails should be authenticated and what they can do if ever that authentication fails.Â
But one of its best features is the email warmup process.Â
Email Warmups
If switching to a new mail server or IP, gradually increase sending volume to avoid triggering spam filters. Warmy.io can automate this process by:
- Slowly increasing email sending volumes.
- Engaging with email recipients to improve trust.
- Boosting domain reputation for better inbox placement.
Many ISPs may have trouble trusting new or inactive email addresses since it does not have any foundation of its reputation.Â
For new domains or inactive mailboxes, email warmup is, therefore, crucial in establishing a trustworthy sender reputation before large-scale outreach.
Warmy’s email warmups process helps establish a positive sender reputation, reducing—but not eliminating—the risk of spam filtering by gradually and automatically increasing the volumes of emails you can send, for up to 5,000 emails per day.Â
Domain Health Hub
One of the other features that is worth taking note is the Warmy’s domain health hub. It contributes to the ideal email hygiene since users obtain complete monitoring of their deliverability at the domain level instead of their individual inboxes.Â
- Instant Domain Health Score: Check your deliverability status with metrics such as Inbox Placement, DNS Authentication, and Google Postmaster Data.
- Clear Warm-Up Performance Insights: Gives you the ability to track spam rates, inbox placement, and deliverability trends weekly and monthly.
- Comprehensive DNS Status Checks: Validate and troubleshoot SPF, DKIM, DMARC, rDNS, MX, and A records for seamless email authentication and security.Â
- Optimized Multi-Domain Monitoring: Manage all your domains from one sleek dashboard. Making it easier to identify which ones need immediate action.Â
- One-Click Deep Insights: Click on any domain to access detailed health metrics, performance reports, including deliverability trends with ease.Â
Email Seed List
Seed listing is one of Warmy’s advanced deliverability systems. It has the flexibility to be integrated into any email client, and improve your email performance testing. Warmy will supply genuine email addresses from Gmail, Outlook, and Yahoo that will act as seeds for testing your email deliverability.Â
It will simulate real engagement to improve sender trust, and if in case that your emails are sent to spam, it will be removed from spam and marked as important to program ISP into understanding that your emails are legitimate.
Customer Success Support, and Deliverability Consultant
We offer 24/7 customer support, via Zoom calls, and chat support, not only for navigating our website, system and tools, but also guarantee that you achieve your long-term goals and acquire reputable emails through our email deliverability programs.Â
Want to improve your email deliverability? Sign up for the 7-day free trial, or book a demo to improve your email deliverability today!
