Email is an instrumental communication tool that finds its advantages in areas such as marketing, customer support, and other internal communication processes.
Email marketing is considered as the “king of all marketing channels”, while email communication for both customer support and internal communication offers a non-time sensitive system allowing everyone without rushing too much of the information.
Here at Warmy.io, we understand the immense value of emails for almost everyone in the professional landscape; giving us the opportunity to implement an All-In-One tool for email deliverability. With our boundless offerings of free tools such as our free email deliverability test. However, we also understand that there are a variety of factors that may affect your email deliverability.
When an email user consistently gets their emails marked as spam, gets rejected by mail servers, or when you understand that your email reputation is suddenly depleting then it is most likely the cause of a Reverse DNS (rDNS) lookup failure.
Reverse DNS helps email servers verify that the sending server’s IP address resolves to a legitimate domain. When this verification fails, mail servers may reject emails, flag them as spam, or lower your sender reputation, impacting your ability to reach inboxes.
Explaining Reverse DNS Lookup and its Importance
rDNS lookup is a procedure that involves mapping an IP address back to its associated domain name. It is a verification process utilized by mail servers to guarantee that the genesis of the email is legitimate and from a trusted source.
Simply put, it helps you identify the domain name associated with the IP address.
How Reverse DNS Lookup Works
When an email is sent, the recipient’s mail server confirms the IP address of the sending server. After that, it performs an rDNS lookup verifying if the IP address then confirms if it has a properly configured Pointer (PTR) record.
If it is properly configured, the email is more likely to be accepted. However, if there are no PTR records or if there is a mismatch between the forward and reverse DNS, then the email may be flagged as suspicious or blocked.
Why rDNS is Crucial for Email Deliverability?
For marketers that perform email outreach on a daily basis having a strong sender reputation is vital. To help establish this reputation, every email user should consider improving their email deliverability. If your emails are being marked as spam, or rejected then that means that mail servers will consider your email as non-reputable.
rDNS are critical for preventing emails from being flagged as spam. As well, reduce email rejections by proving that your mail server has proper configuration. rDNs are also required by some of the biggest and major email providers — Gmail, Microsoft, and Yahoo — for proper email authentication.
Common Causes of Reverse DNS Lookup Failures
Either you have a missing or misconfigured PTR record, or there are some minor or major errors in your DNS mapping, it can contribute to rDNS lookup failures. Let’s explore some of these common causes below:
1. Missing or Misconfigured PTR Record
If your mail server’s IP address does not have a valid PTR record, recipient mail servers cannot verify its authenticity, leading to deliverability issues.
2. Incorrect Forward and Reverse DNS Mapping
Reverse DNS only works correctly when the forward DNS (A record) and reverse DNS (PTR record) match.
3. Sending Emails from Dynamic IP Addresses
Many ISPs assign dynamic IPs, which frequently change and do not have associated PTR records. These emails are often flagged as spam.
4. Blacklisted IP Address
If your IP is blacklisted on spam databases like Spamhaus, Barracuda, or UCEPROTECT, even properly configured rDNS records won’t improve deliverability.
5. ISP or Hosting Provider Restrictions
Some ISPs do not allow customers to configure custom PTR records, preventing proper rDNS setup.
Diagnosing and Fixing Reverse DNS Lookup Failures
If you’ve encountered some of these errors, you can employ the following strategies to help you determine if rDNS is properly configured.
Diagnostics
MXToolbox Reverse Lookup
- Go to MXToolbox rDNS Lookup
- Enter your mail server’s IP address.
- If the result does not return a domain name, your rDNS is misconfigured.
Nslookup Command (Windows/Linux)
Run the following command in Command Prompt or Terminal:
nslookup <your-mail-server-IP>
- If no domain name appears, the PTR record is missing or incorrect.
Dig Command (Linux/macOS)
Run the following:
dig -x <your-mail-server-IP>
- A valid response should return a PTR record with your domain name.
Check Mail Server Logs
Most email servers log authentication failures, spam rejections, and DNS errors related to rDNS lookup failures.
Set Up a Correct PTR Record
- Contact your ISP or hosting provider to add a PTR record for your email server’s IP address.
- The PTR record must match the hostname used in your forward DNS (A record).
Example PTR record:
123.45.67.89.in-addr.arpa. IN PTR mail.yourdomain.com.
Ensure Forward and Reverse DNS Consistency
- The A record for mail.yourdomain.com should point to 123.45.67.89.
- The PTR record for 123.45.67.89 should return mail.yourdomain.com.
Use a Static IP Address for Sending Emails
- If possible, use a dedicated/static IP for your mail server.
- Avoid using residential or ISP-assigned dynamic IPs.
Monitor Blacklists and Request Removal
- Check if your IP is blacklisted using MXToolbox Blacklist Checker.
- Request delisting if your IP has been flagged.
Work with Your ISP or Hosting Provider
- Some hosting providers restrict PTR record edits.
- Contact support to ensure proper rDNS configuration.
Implement SPF, DKIM, and DMARC Authentication
- SPF (Sender Policy Framework): Defines which mail servers can send emails on behalf of your domain.
- DKIM (DomainKeys Identified Mail): Cryptographically signs outgoing emails to verify authenticity.
- DMARC (Domain-based Message Authentication, Reporting, and Conformance): Prevents email spoofing and phishing attempts.
Proper authentication with SPF, DKIM, and DMARC helps reinforce rDNS validation.
Test rDNS After Making Changes
After setting up your PTR record, use the MXToolbox or nslookup command to verify that rDNS resolves correctly.
Warmy: Another Way to Improve Email Deliverability
Warmy.io is known for its free email deliverability test. It provides you with the evaluation of your email’s effectiveness on reaching the recipient’s inboxes.
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.
Domain Health Hub
Warmy’s domain health hub contributes to the ideal email hygiene since users obtain complete monitoring of their deliverability at the domain level instead of their individual inboxes. It offers a multitude of advantages that ensures that your emails are setup for success.
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.
Optimized Multi-Domain Monitoring: Manage all your domains from one sleek dashboard. Making it easier to identify which ones need immediate action.
One-Click Deep Insights: Click on any domain to access detailed health metrics, performance reports, including deliverability trends with ease.
DNS Records Testing
Warmy.io has a DNS records testing which can help you test up to 100 DNS records maintaining an optimal email deliverability. This is vital for confirming if your emails are indeed being received by your recipient and if they are landing on their inboxes.
Inbox Placement Dashboard
Obtain accurate data or reports of where your emails are landing when you send emails to recipients. Warmy’s Inbox placement dashboard helps you determine if your emails are being routed to your recipient’s inbox, spam, unreceived, or promotion.
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.
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.
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. And the most important thing is that with the help of the seed list you can warm up absolutely any email provider, even the one that cannot be warmed up with SMTP — from Gmail, Outlook, and Yahoo that will act as seeds for testing your email deliverability.
- Email opens – Your email is not just marked as read but actually opened and scrolled through to simulate real engagement.
- Link clicks – If your email contains links, our system will click them naturally, improving sender trust.
- Spam recovery – If an email lands in spam, it is manually removed and marked as important to teach ISPs that your emails are legitimate.
- Dynamic email interaction – Instead of a static process, the system engages with your email content, ensuring interactions appear genuine and human-like.
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.
Want to improve your email deliverability? Sign up for the 7-day free trial, or book a demo to improve your email deliverability today!
