How does rDNS impact email deliverability when using dedicated IPs?
Matthew Whittaker
Co-founder & CTO, Suped
Published 21 May 2025
Updated 18 Aug 2025
9 min read
When you're sending emails, especially at scale, dedicated IP addresses often come into play. These IPs are assigned exclusively to you, giving you full control over your sending reputation. Unlike shared IPs, where your deliverability can be affected by other senders' practices, a dedicated IP means your email performance is solely a reflection of your own sending habits.
However, securing a dedicated IP is only one piece of the puzzle. The way your IP address is identified on the internet also plays a crucial role. This is where reverse DNS, or rDNS, steps in. It's a fundamental email authentication record that ensures your sending IP can be traced back to a legitimate domain.
The relationship between rDNS and dedicated IPs is critical for maintaining strong email deliverability. Without proper rDNS configuration, even the most pristine dedicated IP can face challenges getting emails into the inbox. It's a core trust signal that mailbox providers look for.
The role of rDNS in email authentication
Reverse DNS, specifically a PTR record, is essentially the inverse of a regular DNS A record. While an A record translates a domain name into an IP address (e.g., example.com to 192.0.2.1), a PTR record performs the reverse lookup, mapping an IP address back to a domain name (e.g., 192.0.2.1 to mail.example.com). This lookup is a vital step in how receiving email servers verify the legitimacy of incoming messages.
When your email server attempts to deliver a message, the recipient's mail server often performs an rDNS check. This is done to ensure that the IP address sending the email is indeed associated with the domain it claims to be from. If this check fails, or if there's a mismatch between the IP and the domain, it raises a red flag for the receiving server, indicating a potential spam source or misconfiguration.
For dedicated IPs, having a correctly configured rDNS record that points to your sending domain or a subdomain is a strong signal of authenticity. It tells the recipient's server, "This email is coming from a known, verified source," enhancing trust. For a deeper dive into the mechanics, consider reading more about reverse DNS white labeling.
Impact on sender reputation and inbox placement
A properly configured rDNS (or reverse DNS) record is a significant factor in your sender reputation. Mailbox providers, such as Google and Yahoo, weigh rDNS in their algorithms to determine if an email is legitimate or potential spam. If your dedicated IP lacks a valid rDNS entry, or if it points to an unrelated domain, it can negatively impact your sender reputation, making it harder for your emails to reach the inbox. This can lead to your emails being flagged as suspicious or even directly rejected.
In essence, a correct rDNS setup provides a form of forward-confirmed reverse DNS (FCrDNS). This means that the IP address resolves to a hostname, and that hostname, in turn, resolves back to the original IP address. This two-way validation is a robust authentication signal, especially important for dedicated IPs where the expectation is a clear, consistent identity. Without it, your dedicated IP might be treated with the same suspicion as an unauthenticated, shared IP.
Failure to set up rDNS for your dedicated IP can lead to increased bounce rates, emails landing in the spam folder, or even your IP being added to an email blacklist (or blocklist). Some spam filters and corporate mail systems, particularly in B2B environments, perform rigorous rDNS checks and may outright reject emails from IPs without proper FCrDNS. This is part of a broader set of measures, like SPF and DKIM, that collectively build your email's trustworthiness. You can learn more about how SPF, DKIM, DMARC, and dedicated IPs affect deliverability.
For high-volume senders, maintaining a stellar IP reputation is paramount. A properly configured rDNS record is a foundational element for this. It helps mailbox providers accurately assess your sending reputation and ensures your dedicated IP performs as expected. Without this key authentication, other efforts to boost deliverability might be undermined.
Proper rDNS Setup
Trust and authentication: Clearly identifies the sender's IP and domain, building trust with receiving mail servers.
Improved inbox placement: Increases the likelihood of emails landing in the inbox rather than spam folders.
Enhanced IP reputation: Contributes positively to your dedicated IP's reputation with ISPs.
Compliance: Meets a common requirement for many mail servers, reducing rejections.
Misconfigured or missing rDNS
Suspicion and rejection: Mail servers may view emails as spam or outright reject them.
Damaged IP reputation: Leads to a poor reputation for your dedicated IP, even if other factors are good.
Increased spam folder placement: Emails frequently land in spam, reducing engagement and ROI.
Blocklisting risk: Higher chance of your IP being added to public or private blocklists.
Practical implications and common pitfalls
While a dedicated IP provides greater control over your email reputation, the management of its rDNS can sometimes be outsourced to your Email Service Provider (ESP). Many ESPs maintain their own rDNS records for the dedicated IPs they lease to clients. This means that when a recipient server performs an rDNS lookup on your dedicated IP, it might resolve to a domain owned by the ESP, not your own. While often acceptable, it can be a point of consideration for brand purity and potential deliverability nuances.
The primary concern here is if the ESP's domain used for rDNS has a poor reputation. If the ESP has a history of allowing questionable sending practices on their platform, their general domain reputation could indirectly affect your email deliverability, even on a dedicated IP. This is why some clients prefer a fully white-labeled rDNS, where the PTR record points directly to a domain or subdomain of their own. This removes any external branding from the email headers and grants full control over the associated domain's reputation. You can read more about shared rDNS issues for SaaS platforms sending on behalf of clients, which has similar implications.
While an ESP-managed rDNS might be 'fine' in many cases, especially for larger, reputable ESPs who actively manage their sending infrastructure, directly controlling your dedicated IP's rDNS through your own domain is generally a best practice for maximizing deliverability and maintaining brand consistency. It eliminates one potential variable that could impact your email's journey to the inbox.
Best practices for rDNS configuration on dedicated IPs
Align with sending domain: Ensure your PTR record resolves to a hostname that corresponds to your sending domain (e.g., mail.yourdomain.com).
FCrDNS: Verify that the hostname from your PTR record also resolves back to the original IP address via an A record.
Consistent naming convention: Use clear and unambiguous hostnames for your rDNS records, avoiding anything that appears generic or dynamic.
Regular monitoring: Periodically check your rDNS configuration to ensure it remains correct and active.
Advanced considerations and specific ISP requirements
While rDNS is widely accepted as a standard for email authentication, some mail receivers are more stringent than others. Certain ISPs (Internet Service Providers) might treat dynamic rDNS records with heightened suspicion. A dynamic rDNS record typically changes frequently, which is often associated with residential internet connections or less secure servers. For dedicated IPs, the expectation is a static, stable rDNS that clearly identifies the sending entity. If your ESP's rDNS configuration appears dynamic, it could lead to stricter filtering by some demanding receivers.
Specific nuances can arise with certain mailbox providers. For instance, some senders have observed that T-Online.de recipients may experience deliverability issues if the rDNS is not explicitly non-default or aligned with the sender's domain. While not a universal rule, such specific requirements highlight the importance of understanding the landscape of different mail servers' preferences and policies. Google's own email sender guidelines explicitly recommend setting up valid reverse DNS records.
Ultimately, while a missing or misconfigured rDNS might not be the sole cause of deliverability failure, it's a significant contributing factor. It can increase your IP's risk of being added to a blacklist, hinder your ability to bypass sophisticated spam filters, and generally erode trust with receiving mail servers. Always ensuring your dedicated IP has a proper and stable rDNS setup is a fundamental step towards optimal email deliverability.
Example: Check rDNS for an IP Addressbash
dig -x 192.0.2.1 PTR
Views from the trenches
Best practices
Always ensure your dedicated IP's rDNS points to a hostname within your controlled domain.
Verify that your PTR record is configured for FCrDNS (forward-confirmed reverse DNS) to enhance trust.
Choose a clear and consistent naming convention for your rDNS hostname.
Common pitfalls
Relying solely on your ESP's default rDNS if their domain has a questionable reputation.
Having a dynamic rDNS record that changes frequently, causing suspicion with mail servers.
Ignoring rDNS setup entirely, leading to emails being flagged as spam or rejected.
Expert tips
For B2B sending, strict corporate filters (like Proofpoint) often demand perfect rDNS alignment.
Even if your ESP manages rDNS, confirm the underlying domain's reputation for potential impact.
Consider white-labeling rDNS if brand purity and absolute control are paramount for your email program.
Marketer view
Marketer from Email Geeks says that while a misaligned rDNS record on its own may not cause massive issues, it can contribute to deliverability problems when combined with other red flags, especially in B2B scenarios.
January 22, 2024 - Email Geeks
Expert view
Expert from Email Geeks says that many ESPs use their own rDNS even for dedicated IPs, and as long as the IP resolves to a domain name, and that domain name resolves back to the IP, it is generally acceptable.
January 22, 2024 - Email Geeks
Conclusion: The undeniable importance of rDNS
For email senders utilizing dedicated IP addresses, reverse DNS (rDNS) is more than just a technical detail, it's a foundational element of email deliverability. It serves as a crucial authentication mechanism, allowing recipient mail servers to verify the legitimate origin of your emails. Without it, even the cleanest dedicated IP can struggle to establish the necessary trust with ISPs and spam filters.
While some ESPs manage rDNS for their clients, opting for a white-labeled rDNS that points to your own domain provides the highest degree of control and brand consistency. It eliminates potential reputation risks associated with shared ESP infrastructure and ensures your dedicated IP's identity is unequivocally tied to your brand. This level of alignment is particularly important for high-volume senders and those targeting B2B recipients, where mail servers often apply stricter verification processes.
In summary, proper rDNS configuration for your dedicated IP isn't just a recommendation, it's a critical component for maintaining a healthy sender reputation and achieving optimal inbox placement. Regularly checking and confirming your rDNS setup is a simple yet powerful step to safeguard your email deliverability and ensure your messages reach their intended audience reliably.
Google and 
Yahoo, weigh rDNS in their algorithms to determine if an email is legitimate or potential spam. If your dedicated IP lacks a valid rDNS entry, or if it points to an unrelated domain, it can negatively impact your sender reputation, making it harder for your emails to reach the inbox. This can lead to your emails being flagged as suspicious or even directly rejected.
