Summary
Updating reverse DNS (rDNS) on an MTA generally has minimal impact if done correctly. Key is ensuring the EHLO hostname and SPF entries match after the update. Accurate DNS records, including PTR records that map IPs to hostnames, are crucial for email server reputation, deliverability, and authentication. PTR records help verify the legitimacy of the sending server and show the IP has been legitimately assigned. Inconsistent forward (A) and reverse (PTR) records may cause authentication failures and distrust from mail servers, potentially leading to emails being rejected or marked as spam. Consider the domain's age and TLD, as newer domains may cause issues. Changes can take up to 72 hours to propagate. Proper setup avoids RBL listings. Ensure consistent DNS records and a valid PTR record pointing to your domain.
Key findings
- rDNS impact: Updating rDNS is generally low impact when performed correctly.
- Key DNS Alignment: EHLO hostname/SPF alignment post-update is important for authentication.
- PTR Importance: Valid PTR records mapping IP to hostname are crucial for verification.
- A/PTR Consistency: Matching forward (A) and reverse (PTR) records are essential.
- Domain reputation: Properly configured rDNS improves sender reputation and deliverability.
Key considerations
- Accuracy: Prioritize accurate configuration for the rDNS update.
- Domain considerations: Consider the domain age/TLD; newer domains might encounter problems.
- Propagation: Allow up to 72 hours for DNS changes to propagate.
- RBL Avoidance: Proper setup prevents being listed on RBLs.
- Correct PTR record: Ensure PTR points back to correct hostname & verify with a DNS lookup.
What email marketers say
10 marketer opinions
Updating reverse DNS (rDNS) on an MTA is crucial for email deliverability and sender reputation. Ensuring the EHLO hostname and SPF entries match after the update is essential, as some systems assign reputation based on the hostname. Proper setup, including a valid PTR record pointing to your domain, helps establish trust with receiving mail servers, validates your server's identity, and reduces the likelihood of emails being marked as spam. Consistency between forward and reverse DNS records (A and PTR records) is vital to prevent authentication failures. Consider the domain age and TLD, as newer domains and gTLDs may cause issues. Changes can take up to 72 hours to propagate, during which some mail servers may not recognize the updated record. It is important to do it correctly the first time to avoid automated listings on RBLs. Verify that the A record matches the hostname in the PTR record.
Key opinions
- rDNS Importance: rDNS is crucial for email deliverability and sender reputation.
- EHLO/SPF Alignment: Ensure EHLO hostname and SPF entries match after updating rDNS.
- PTR Record Validity: A valid PTR record pointing to your domain is essential.
- Domain Reputation: Some systems assign reputation based on hostname, so maintain a good reputation.
- Forward/Reverse DNS Consistency: Maintain consistency between forward and reverse DNS records (A and PTR).
Key considerations
- Domain Age/TLD: Consider the age and TLD of the new domain, as newer ones may cause issues.
- Propagation Time: rDNS changes can take up to 72 hours to propagate.
- RBL Listings: Incorrect setup can lead to automated listings on RBLs, impacting deliverability.
- Initial Setup Accuracy: Ensure the initial setup is correct to avoid issues.
- PTR Record Verification: Manually check for only one PTR record for the IP.
Marketer view
Email marketer from SparkPost shares that setting up reverse DNS is a fundamental step in improving email deliverability. It helps validate the sending server's identity and reduces the likelihood of emails being marked as spam.
15 Jun 2025 - SparkPost
Marketer view
Email marketer from Email Geeks shares that ensuring the EHLO hostname/SPF entry matches is important, otherwise it may cause issues. They also expect that some places would assign reputation based on the hostname.
23 May 2024 - Email Geeks
What the experts say
3 expert opinions
Updating reverse DNS (rDNS) should have minimal impact if done correctly, emphasizing the importance of accurate configuration to avoid issues. A critical aspect is ensuring that forward and reverse DNS records (A and PTR records) match. Inconsistent records can lead to authentication failures and lack of trust from receiving mail servers. Specifically, the absence of a PTR record or a mismatch with the hostname can result in emails being rejected or marked as spam. PTR records serve as proof that an IP address is legitimately assigned to a mail server.
Key opinions
- Impact of Update: Updating rDNS should have minimal impact if done correctly.
- DNS Record Consistency: Matching forward and reverse DNS records (A and PTR records) is crucial.
- PTR Record Importance: PTR records validate that an IP address is legitimately assigned to a mail server.
- Authentication Impact: Inconsistent DNS records can lead to authentication failures and lack of trust.
Key considerations
- Correct Configuration: Ensure accurate configuration during the rDNS update to prevent issues.
- PTR Record Presence: Verify the presence of a PTR record pointing to your mail server's hostname.
- Matching Records: Ensure the hostname in the PTR record matches the hostname used by the mail server.
- Deliverability: Absence of or mismatch in PTR record can cause emails to be rejected or marked as spam.
Expert view
Expert from Word to the Wise explains that ensuring forward and reverse DNS records match is crucial. Inconsistent records may cause authentication failures, and email servers may not trust messages from such sources. Therefore, it's best practice to maintain identical records for A and PTR lookups.
3 Jul 2023 - Word to the Wise
Expert view
Expert from Spam Resource responds that if your mail server doesn't have a PTR record, or the PTR record doesn't match the hostname used by the mail server, many receiving servers will reject your email or mark it as spam. A PTR record shows that the IP address has been legitimately assigned to a mail server.
11 Jan 2022 - Spam Resource
What the documentation says
4 technical articles
Properly configured PTR records, which map IP addresses to hostnames, are crucial for email server reputation and deliverability. They help verify the legitimacy of the sending server. Accurate DNS records, including PTR records, are essential for ensuring email delivery. Incorrect or missing PTR records can lead to emails being flagged as spam. Configuration guidelines emphasize ensuring the hostname matches the forward DNS record and that the PTR record points back to the correct hostname to avoid email delivery issues. RFC 1035 outlines PTR record requirements essential for reverse DNS lookups, crucial for email deliverability and authentication, though it doesn't directly address email specifics.
Key findings
- PTR Records Define: PTR records map IP addresses to hostnames.
- PTR Records Importance: Properly configured PTR records are crucial for email server reputation and deliverability.
- DNS Accuracy: Accurate DNS records, including PTR records, are essential for email delivery.
- RFC 1035 Standards: RFC 1035 outlines PTR record requirements essential for reverse DNS lookups.
Key considerations
- Legitimacy Verification: PTR records help verify the legitimacy of the sending server.
- Spam Prevention: Incorrect or missing PTR records can lead to emails being flagged as spam.
- Hostname Matching: Ensure the hostname matches the forward DNS record and that the PTR record points back to the correct hostname.
- RFC 1035 Relevance: Use RFC 1035 for PTR record guidance and the proper reverse DNS setups.
Technical article
Documentation from DigitalOcean Community provides a detailed guide on configuring reverse DNS for a server. It advises ensuring the hostname matches the forward DNS record and that the PTR record points back to the correct hostname to avoid email delivery issues.
28 Jan 2024 - DigitalOcean Community
Technical article
Documentation from Microsoft Learn explains that PTR records, also known as reverse DNS records, map an IP address to a hostname. Properly configured PTR records are crucial for email server reputation and deliverability, as they help verify the legitimacy of the sending server.
11 Mar 2025 - Microsoft Learn
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