How does rDNS impact email deliverability when using dedicated IPs?

Summary

Reverse DNS (rDNS) is a critical component of email deliverability when using dedicated IPs. Technical documentation highlights that a matching PTR record for the sending IP address, aligned with the hostname in the HELO/EHLO greeting, is essential. A properly configured rDNS verifies the identity of the sending server, establishing trust with ISPs and improving sender reputation. Without a valid rDNS, emails are more likely to be flagged as spam or rejected. While client-specific rDNS is preferred for branding, some ESPs use their own, which is acceptable if forward and reverse DNS resolution works. A good domain reputation is crucial for rDNS, as a poor reputation can negatively impact deliverability. Experts agree that while rDNS is important, it's not a complete solution, and other factors play a significant role. Dynamic rDNS records may raise suspicion.

Key findings

  • PTR Record Required: A matching PTR record (reverse DNS) is required for the sending IP address, aligning with the HELO/EHLO greeting.
  • Trust and Reputation: rDNS helps establish trust with ISPs and improve sender reputation, reducing the likelihood of emails being marked as spam.
  • Negative Impact: Not having a correct rDNS record can cause delivery problems, leading to rejection or spam categorization.
  • ESP Considerations: ESPs can use their own rDNS for dedicated IPs if forward and reverse DNS resolution works, but client-specific rDNS is preferred for branding.
  • Domain Reputation Matters: The domain used in the rDNS should have a good reputation to avoid negatively impacting deliverability.
  • Essential But Not Sufficient: A correct rDNS is important, but it's not a guarantee of inbox placement; other factors also play a role.
  • Antispam Technique: Reverse DNS lookup is a common anti-spam technique to verify sender identity.

Key considerations

  • Configuration Accuracy: Ensure the PTR record is accurately configured and matches the sending IP address and hostname.
  • Forward/Reverse Consistency: Maintain consistency between the PTR record and forward DNS records.
  • Brand control: Determine how important it is for you to control the branding shown in headers.
  • Monitor setup: Without correct rDNS configuration, emails will be automatically treated as spam
  • Ongoing Maintenance: Regularly monitor sender reputation and deliverability metrics to ensure the rDNS configuration remains effective.
  • Beyond rDNS: Understand that rDNS is just one factor in deliverability and other factors also play a significant role.

What email marketers say
11Marketer opinions

Reverse DNS (rDNS) plays a crucial role in email deliverability, particularly when using dedicated IPs. A properly configured rDNS record verifies the identity of the sending server, establishing trust with ISPs and improving sender reputation. Without a valid rDNS, emails are more likely to be flagged as spam or rejected by receiving mail servers. Dynamic rDNS records may raise suspicion, and a domain with a poor reputation used in the rDNS can negatively impact deliverability. Therefore, setting up rDNS is a best practice to ensure emails reach the intended recipients' inboxes.

Key opinions

  • Trust & Reputation: rDNS helps establish trust with ISPs and improves sender reputation by verifying the legitimacy of the sending server's IP address.
  • Spam Prevention: Without a valid rDNS record, emails are more likely to be flagged as spam or rejected outright by receiving mail servers.
  • Dynamic rDNS: Some mail receivers treat dynamic rDNS records with suspicion, potentially impacting deliverability.
  • Domain Reputation: The domain used in the rDNS record should have a good reputation; a domain with a poor reputation can negatively impact deliverability.
  • Verification: rDNS ensures the connection attempts by the server are genuine, gaining trust and raising the IP address's reputation.

Key considerations

  • Configuration: Ensure rDNS records are properly configured to match the sending domain and IP address.
  • ESP Competence: If using an ESP, verify they use rDNS records that do not appear dynamic and maintain a good reputation.
  • Regular Monitoring: Monitor sender reputation and deliverability metrics to ensure the rDNS configuration remains effective.
  • Essential for Dedicated IPs: Setting up rDNS is particularly crucial when using dedicated IPs to establish a verified identity for the email server.
Marketer view

Email marketer from Mailjet explains that rDNS helps to establish trust with ISPs and improve deliverability. It confirms that the IP address is associated with a legitimate domain, which makes it less likely for emails to be marked as spam. Setting up rDNS is a best practice for dedicated IPs.

October 2021 - Mailjet
Marketer view

Email marketer from Super User explains that if you send email from a server with no reverse DNS record, many mail servers will classify the email as spam. Creating a reverse DNS record for your mail server's IP address will drastically increase your deliverability.

January 2025 - Super User
Marketer view

Email marketer from Email Geeks shares that some mail receivers do treat dynamic rDNS records with suspicion, but a competent ESP should have a record that doesn't appear dynamic.

May 2023 - Email Geeks
Marketer view

Email marketer from Easyspace explains that reverse DNS (rDNS) helps in email delivery by verifying the identity of the server sending the email. It also helps in reducing spam and helps your email get delivered and reach your target customer.

September 2021 - Easyspace
Marketer view

Email marketer from StackOverflow shares that many email servers will reject connections from servers without reverse DNS. Set it or suffer.

May 2022 - StackOverflow
Marketer view

Email marketer from Email Geeks believes that the issue could only happen if the domain used in the rDNS is having a bad reputation already.

June 2022 - Email Geeks
Marketer view

Email marketer from Reddit explains that having a properly configured rDNS record is like having a verified identity for your email server. It tells receiving servers that you are who you say you are, which can significantly improve your chances of landing in the inbox rather than the spam folder. If you're using dedicated IPs, setting up rDNS is a must.

December 2022 - Reddit
Marketer view

Email marketer from DigitalOcean explains that reverse DNS (rDNS) is the resolution of an IP address to a domain name, the opposite to forward DNS resolution. rDNS is commonly used to verify the legitimacy of a server's IP address, typically for email servers. Many email service providers will reject emails that come from IP addresses without rDNS configured, or whose rDNS entries don't match the sending domain.

October 2024 - DigitalOcean
Marketer view

Email marketer from SendGrid responds that rDNS is an important factor in email deliverability because it provides a way for receiving mail servers to verify the identity of the sending server. Without a valid rDNS record, emails are more likely to be flagged as spam or rejected outright. Setting up a reverse DNS record for your sending IP address helps to build trust with receiving mail servers and improve your deliverability rates.

August 2021 - SendGrid
Marketer view

Email marketer from SparkPost shares that a properly configured rDNS record is essential for maintaining a positive sender reputation. It helps to verify the identity of the sending server and can prevent emails from being blocked or filtered as spam. They recommend that all senders using dedicated IPs should configure rDNS.

November 2021 - SparkPost
Marketer view

Email marketer from Namecheap explains that setting up a reverse DNS record for your server IP can help prevent your emails from being flagged as spam. Reverse DNS ensures that the connection attempts by the server are genuine, which is the key point in gaining trust and raising the reputation of the IP address. With reverse DNS configured, more mail servers will positively treat your messages and allow them to get to the recipient's inbox.

July 2023 - Namecheap

What the experts say
4Expert opinions

Experts generally agree that while a correct rDNS record is important for email deliverability, it's not a guarantee of inbox placement. Not having a properly configured rDNS can definitely cause delivery problems. Some ESPs use their own rDNS even for dedicated IPs, which is generally fine as long as the IP resolves correctly to the domain name and back. Client-specific rDNS is often preferred for branding purposes, to remove any trace of the ESP, but it places responsibility on the client for maintaining the DNS records. A PTR record is a basic requirement for being considered legitimate by many receivers, especially when using dedicated IPs.

Key opinions

  • rDNS Importance: A correct rDNS record is important for email deliverability, but it's not a complete solution.
  • Negative Impact: Not having a correct rDNS record can cause delivery problems.
  • ESP rDNS: ESPs can use their own rDNS for dedicated IPs as long as forward and reverse DNS resolution works.
  • Client Branding: Client-specific rDNS is often for branding purposes, removing ESP branding from headers.
  • PTR Requirement: A PTR record is a basic requirement for good deliverability with dedicated IPs.

Key considerations

  • DNS Resolution: Ensure that forward and reverse DNS resolution (IP -> domain name -> IP) works correctly.
  • Client Responsibility: If using client-specific rDNS, be prepared to maintain the DNS records and keep them accurate.
  • Basic Requirement: Prioritize setting up a valid PTR record for dedicated IPs to meet basic deliverability requirements.
  • Beyond rDNS: Understand that rDNS is just one factor in deliverability; other factors also play a significant role.
Expert view

Expert from Word to the Wise emphasizes that a PTR record must exist and be associated with the IP address for your mail server to be considered legitimate by many receivers. This is a basic requirement for good deliverability, especially when using dedicated IPs.

November 2023 - Word to the Wise
Expert view

Expert from Email Geeks shares that the main reason to do client-specific, white label reverse DNS is for clients who want no trace of any brand other than theirs in the email headers, rather than anything technical. If the reverse DNS points to hostnames in the client's domain, the ESP relies on the client to do any needed updates.

March 2023 - Email Geeks
Expert view

Expert from Spam Resource states that having a correct rDNS is important, but it is not sufficient to get your mail delivered. He elaborates that not having a correct rDNS can definitely cause delivery problems.

August 2022 - Spam Resource
Expert view

Expert from Email Geeks explains that it's probably fine for ESPs to use their own rDNS even for dedicated IPs, as long as the IP -> domain name -> IP works. One of her clients has dedicated IPs and half have rDNS pointing to their domain and half rDNS pointing to the ESP.

September 2023 - Email Geeks

What the documentation says
5Technical articles

Technical documentation consistently emphasizes the necessity of correctly configured rDNS (PTR) records for email servers. A matching PTR record is required for the sending IP address, aligning with the hostname in the HELO/EHLO greeting. Without this match, emails are more likely to be flagged as spam or rejected. Reverse DNS lookups are a common anti-spam technique, verifying the sender's identity. Lack of a PTR record, or discrepancies between the PTR record and forward DNS, raise suspicion. rDNS guarantees email server authenticity, and its absence often leads to automatic categorization as spam. rDNS facilitates verification that the sender is who they claim to be, enhancing email legitimacy.

Key findings

  • PTR Record Required: A matching PTR record (reverse DNS) is required for the sending IP address.
  • HELO/EHLO Alignment: The PTR record must match the hostname specified in the HELO or EHLO greeting.
  • Anti-Spam Technique: Reverse DNS lookup is a common anti-spam technique.
  • Sender Verification: rDNS allows a mail server to verify that a sender is who they claim to be.
  • Authenticity Guarantee: rDNS records are an important criterion for reverse DNS lookups to guarantee the authenticity of an email server.

Key considerations

  • Configuration Accuracy: Ensure the PTR record is accurately configured to match the sending IP address and hostname.
  • Forward/Reverse Consistency: Maintain consistency between the PTR record and forward DNS records.
  • Avoid Rejection: Configure rDNS records to avoid email rejection or spam categorization by receiving mail servers.
  • Sender Reputation: Recognize rDNS as a critical component of establishing and maintaining a positive sender reputation.
  • Monitor setup: Lack of a rDNS record will likely mean your emails are automatically treated as spam.
Technical article

Documentation from Exa Infrastructure shares that rDNS allows a mail server to verify that a sender is who they claim to be. This is done by performing a reverse DNS lookup on the IP address of the sending mail server and comparing the hostname returned to the domain name used in the email's "From" address. If the two match, it increases the likelihood that the email is legitimate.

July 2024 - Exa Infrastructure
Technical article

Documentation from Google Workspace Admin Help explains that a matching PTR record (reverse DNS) is required for the sending IP address. The PTR record must match the hostname specified in the HELO or EHLO greeting. If there's no matching PTR record, or if the hostname in the PTR record doesn't match the sending hostname, the message might get marked as spam.

July 2023 - Google Workspace Admin Help
Technical article

Documentation from RFC Editor recommends that every internet-reachable host should have a reverse address record (PTR) in the in-addr.arpa domain. Failing to configure accurate PTR records can lead to email being rejected by some mail servers.

September 2021 - RFC Editor
Technical article

Documentation from Microsoft Learn indicates that reverse DNS lookup is a common anti-spam technique. Many mail servers perform reverse DNS lookups to verify the hostname associated with the sending IP address. If no PTR record is found, or if it doesn't match the forward DNS record, the email might be considered suspicious.

July 2022 - Microsoft Learn
Technical article

Documentation from Hetzner details that rDNS records are an important criteria for reverse DNS lookups. This is done to guarantee the authenticity of an email server. If no rDNS record exists for an IP address, many mail servers automatically categorize emails as spam.

August 2022 - Hetzner Docs