Summary
Reverse DNS (rDNS) is a critical element for email authentication, deliverability, and sender reputation. It involves mapping an IP address to a domain name (PTR record), allowing receiving mail servers to verify the sender's legitimacy. For shared IPs, rDNS should identify the ESP, while for dedicated IPs, it should identify either the sender or the ESP. It's crucial to avoid including the IP address directly in the rDNS record. A common indicator of spammy ESPs is an rDNS that doesn't connect to their organization, where the resolved domain doesn't lead to the ESP or sender's website. For self-managed servers, configure rDNS to point to your mail server's IP and ensure it matches your sending domain. Properly configured rDNS improves deliverability, helps in trust building, prevents spoofing, and avoids spam flags. Third-party tools can be used to validate rDNS configuration regularly. Consistent EHLO, HELO, and rDNS domains are essential, particularly for IPv6. Without a proper rDNS setup, ISPs and email providers may assume you are not a legitimate sender, leading to deliverability issues. Amazon SES users should ensure correct rDNS configuration, although it's handled by Microsoft for Exchange Online users.
Key findings
- rDNS Purpose: Reverse DNS verifies that a mail server is authorized to send emails for a particular domain by mapping an IP to a domain.
- Shared vs. Dedicated: Shared IPs: rDNS should identify the ESP. Dedicated IPs: rDNS should identify the sender or ESP.
- Spam Identification: Spammy ESPs often use rDNS records that do not connect back to the ESP or sender.
- Authentication Component: rDNS is an essential component of email authentication, helping to establish trust and legitimacy in the email ecosystem.
- Importance: Proper rDNS setup significantly improves email deliverability, trust, and sender reputation.
- Configuration Responsibility: For self-managed servers, configuring rDNS falls to the server owner. ESPs usually manage rDNS for shared IPs.
- MX Record: rDNS is also related to MX records and ensures the mail exchanger is correctly identified.
Key considerations
- Match the Domain: Ensure the rDNS record matches the sending domain to maintain positive sender reputation and improve deliverability.
- Third-Party Validation: Regularly use third-party tools to validate rDNS configuration to confirm accuracy and proper setup.
- Consistent Domains: Ensure EHLO, HELO, and reverse DNS domains are consistent, especially when using IPv6 addresses.
- No IP Addresses: Avoid including direct IP addresses in the rDNS record to prevent being flagged as spam.
- Hosting Coordination: Coordinate with your ISP or hosting provider to ensure the correct rDNS setup, especially for dedicated IPs.
- Microsoft handling: For Exchange Online, Microsoft handles rDNS setup; for other platforms, configuration is the user's responsibility.
- Sender Reputation: Implement and maintain rDNS properly to establish and maintain a positive sender reputation.
What email marketers say
8 marketer opinions
Reverse DNS (rDNS) is a critical component for email deliverability. It involves mapping an IP address back to a domain name, allowing receiving mail servers to verify that the sending server is authorized to send emails for that domain. Proper rDNS configuration builds trust, improves sender reputation, and reduces the likelihood of emails being flagged as spam. For dedicated IPs, the domain owner can often request the ISP or hosting provider to set up the rDNS record to point to their domain. For shared IPs, the ESP typically manages the rDNS. A missing or incorrect rDNS record can increase the spam score and cause emails to be delivered to the junk folder.
Key opinions
- Verification: Reverse DNS verifies that the IP address is associated with the domain sending the email.
- Deliverability: Properly configured rDNS improves email deliverability and reduces the chance of being marked as spam.
- Trust: rDNS helps in establishing trust with receiving mail servers.
- Configuration: For dedicated IPs, the domain owner can often request the ISP or hosting provider to set up the rDNS record.
- Management: For shared IPs, the ESP typically manages the rDNS.
- Spam Score: Missing or incorrect rDNS can increase spam scores and affect inbox placement.
Key considerations
- Matching Domains: Ensure the rDNS record matches the sending domain to avoid being flagged as spam.
- Shared vs. Dedicated: Configuration differs between shared and dedicated IPs; understand who manages the rDNS.
- ISP/ESP Coordination: Coordinate with your ISP or ESP to ensure proper rDNS setup.
- Reputation Impact: Understand that rDNS impacts sender reputation and overall email deliverability.
- Proactive Monitoring: Monitor rDNS records to ensure they remain accurate and properly configured.
Marketer view
Email marketer from MXToolbox Forum responds that reverse DNS records are checked by spam filters to verify the sender's legitimacy. A missing or incorrect reverse DNS record can increase the spam score, causing emails to be delivered to the junk folder. They recommends ensuring the reverse DNS record matches the sending domain to avoid being flagged as spam.
10 Mar 2024 - MXToolbox Forum
Marketer view
Email marketer from Reddit explains that reverse DNS validates the sender's identity, establishing trust with receiving servers. They answer that it helps prevent spoofing and phishing attacks, ensuring that only authorized senders can use the domain. This contributes to better deliverability and protects the sender's reputation.
20 Oct 2022 - Reddit
What the experts say
8 expert opinions
Reverse DNS (rDNS) is crucial for email authentication and deliverability. For shared IPs, rDNS should identify the ESP, while for dedicated IPs, it should identify the sender or the ESP. It should not contain IP addresses directly. Spammy ESPs often use rDNS that doesn't connect to them; the domain in the rDNS should lead to the sender's or ESP's webpage. Matching EHLO, HELO, and rDNS domains is vital, especially with IPv6. A valid rDNS is essential for building IP reputation and proving legitimacy as a sender. Without proper rDNS, ISPs might assume you're not a legitimate sender, leading to deliverability issues and spam flags.
Key opinions
- Shared vs. Dedicated IPs: rDNS for shared IPs should identify the ESP; for dedicated IPs, it should identify the sender or ESP.
- Spammy ESP Identification: Spammy ESPs may use rDNS that doesn't link back to their organization; the rDNS domain should resolve to the sender or ESP's website.
- Domain Matching: EHLO, HELO, and rDNS domains should match for improved identification, especially with IPv6.
- IP Reputation: Proper rDNS is vital for building a positive IP reputation and proving legitimacy as a sender.
- Email Authentication: rDNS is an essential component of email authentication, helping receiving mail servers verify the sender's authorization.
Key considerations
- Reverse DNS Content: Ensure rDNS doesn't contain direct IP addresses and clearly identifies the responsible party (ESP or sender).
- ESP Selection: Evaluate ESPs based on their rDNS practices; a transparent and identifiable rDNS is a positive sign.
- IPv6 Compliance: Maintain consistency across EHLO, HELO, and rDNS domains, especially when using IPv6.
- Reputation Maintenance: Prioritize proper rDNS configuration to build and maintain a positive IP reputation.
- SES Considerations: If using Amazon SES, ensure rDNS is correctly configured; if not, alternative configurations may be needed.
Expert view
Expert from Word to the Wise shares that IP reputation is built by proving you are a legitimate sender over a period of time. One of these factors is Reverse DNS. They explain that without it, ISPs will assume you are not a legitimate sender.
24 Dec 2022 - Word to the Wise
Expert view
Expert from Spam Resource (Steve Linford) explains that reverse DNS (rDNS) is an essential component of email authentication. It involves setting up a PTR record, which maps an IP address back to a domain name. This helps receiving mail servers verify that the server sending the email is authorized to do so. Without proper rDNS, emails are more likely to be flagged as spam, as it's a crucial factor for establishing trust and legitimacy in the email ecosystem.
22 Sep 2024 - Spam Resource
What the documentation says
4 technical articles
Configuring reverse DNS (rDNS) is vital for email deliverability. Microsoft handles rDNS configuration for Exchange Online. However, if you manage your own email servers, you must configure rDNS records to point to your mail server's IP address. The rDNS record should match the domain from which you're sending email, and point to your domain for AWS EC2 instances. For Hetzner servers, rDNS can be configured in their web interface. Properly configured rDNS verifies that your mail server is authorized to send emails from your domain, improving deliverability and preventing emails from being marked as spam.
Key findings
- Verification: rDNS verifies that your mail server is authorized to send emails from your domain.
- Domain Match: Your rDNS record should match the domain from which you're sending email.
- Deliverability Improvement: Properly configured rDNS improves email deliverability and avoids spam flags.
- AWS EC2 setup: For AWS EC2 instances, set the rDNS record to point to your domain.
- Hetzner Configuration: Hetzner servers allow rDNS configuration through their Robot web interface.
Key considerations
- Self-Managed Servers: Ensure you properly configure rDNS if you manage your own email servers.
- Matching Domains: Confirm your rDNS record matches the sending domain to maintain a positive sender reputation.
- Cloud Provider Instructions: Follow specific instructions from your cloud provider (AWS, Hetzner, etc.) for rDNS configuration.
- Dynamic IPs: Consider the implications of dynamic IPs on rDNS configuration and potential deliverability issues.
- Third-Party Validation: Regularly validate your rDNS configuration using third-party tools to ensure accuracy.
Technical article
Documentation from Microsoft Learn explains that for Exchange Online, Microsoft handles the reverse DNS configuration. Customers using their own email servers need to configure reverse DNS records to point to their mail server's IP address. This helps verify that the mail server is authorized to send emails from your domain.
14 Jan 2022 - Microsoft Learn
Technical article
Documentation from Hetzner explains that reverse DNS can be configured in the Hetzner Robot web interface for your servers. You should configure it to point to your domain name. This helps with email deliverability.
9 Jun 2022 - Hetzner Docs
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