Summary
Reverse DNS (rDNS) failure bounces from AT&T (ATT) stem from ATT's stringent requirement for a properly configured and verifiable rDNS record, particularly the PTR record, which maps IP addresses to domain names. These records are essential for ATT to verify the authenticity of sending servers and prevent spam. Failures can be caused by missing, misconfigured, or non-matching PTR records, recent IP address changes causing propagation delays, shared IPs being blacklisted, mismatches between the sending server's hostname and rDNS record, and ATT systems experiencing temporary issues. Properly setting up rDNS, ensuring a match between forward and reverse records, and monitoring for blacklisting are vital steps. While some incidents might be localized or temporary, configuring the rDNS and PTR records correctly are key to resolving the issues.
Key findings
- rDNS Verification: AT&T requires a verifiable rDNS record, especially a PTR record, to accept emails.
- PTR Record Problems: Missing, misconfigured, or non-matching PTR records are the primary cause of bounces.
- Forward/Reverse Match: Matching forward and reverse DNS records strengthen sender reputation and deliverability.
- Propagation Delays: Recent IP changes can lead to temporary failures until DNS records propagate fully.
- Shared IP Risks: Shared IP addresses might be blacklisted, impacting deliverability even with proper settings.
- Hostname Mismatch: Mismatches between the sending server's hostname and rDNS record can trigger rejections.
- Localized Issues: Failures can sometimes be localized to specific nodes or parts of an ESP infrastructure.
- ATT Issues: Temporary glitches on ATT's side can cause transient rDNS lookup failures.
Key considerations
- PTR Record Setup: Ensure that your sending IP address has a properly configured PTR record pointing to your sending domain.
- DNS Consistency: Verify that forward and reverse DNS records match to strengthen sender authentication.
- Contact ISP: Contact your ISP or hosting provider to set up or verify rDNS records, as they manage these records.
- Blacklist Monitoring: Regularly check if your IP address is on any email blacklists and take necessary remediation steps.
- Monitor Deliverability: Continuously monitor email deliverability to AT&T to detect and address any ongoing issues promptly.
- Contact ATT Support: If issues persist despite proper configuration, reach out to AT&T's support for further investigation and assistance.
- Domain Authentication: Ensure domain authentication with SPF, DKIM and DMARC are also configured.
What email marketers say
12 marketer opinions
Reverse DNS (rDNS) failure bounces from AT&T (ATT) typically occur because ATT's systems require a properly configured and verifiable rDNS record to accept emails. Several factors can contribute to these failures, including missing or misconfigured PTR records, recent IP address changes that haven't fully propagated, mismatches between the sending server's hostname and the rDNS record, shared IP addresses being blacklisted, and occasional glitches on AT&T's end. Some reports indicated the issue was isolated to specific nodes or was a widespread issue that AT&T resolved. The resolution involves ensuring that your sending IP address has a PTR record pointing to your sending domain, contacting your ISP or hosting provider to set up or verify the rDNS record, checking if your IP address is blacklisted, and confirming that the forward and reverse DNS records match.
Key opinions
- rDNS Requirement: AT&T requires a valid reverse DNS (rDNS) record for accepting emails, acting as an identifier of permission to send.
- PTR Record Issues: Missing, misconfigured, or mismatched PTR records are a primary cause for rejections.
- Propagation Delays: Recent IP changes may cause temporary failures until DNS records fully propagate.
- Shared IP Risks: Shared IP addresses may be blacklisted, affecting deliverability even with correct configurations.
- Node-Specific Issues: Deliverability issues can be isolated to certain sending nodes.
- Reported Resolution: There have been reports from within Email Geeks that a known rDNS issue with ATT has been resolved.
Key considerations
- PTR Record Validation: Verify the PTR record for your sending IP address using online tools to ensure it matches your sending domain.
- ISP/Hosting Provider: Contact your ISP or hosting provider to set up or verify the rDNS record, as they control DNS records.
- Blacklist Monitoring: Check if your IP address is on any email blacklists and take necessary steps to remove it.
- DNS Consistency: Ensure that forward and reverse DNS records match to strengthen sender reputation.
- Temporary Issues: Be aware that occasional glitches on AT&T's end can cause transient failures.
- Contact ATT: Contact ATT to address the rejections if you have done all you can and they persist.
Marketer view
Email marketer from Email Geeks indicates that the issue might be isolated to three specific nodes: <http://250-flph824.prodigy.net|250-flph824.prodigy.net>, <http://250-alph763.prodigy.net|250-alph763.prodigy.net>, and <http://250-alph753.prodigy.net|250-alph753.prodigy.net>.
2 Feb 2022 - Email Geeks
Marketer view
Email marketer from Sendgrid responds that reverse DNS records are necessary to prove that your sending IP has permission to send using your sending domain. If ATT isn't sure if your IP has permission, they will reject it.
26 Jul 2024 - Sendgrid
What the experts say
5 expert opinions
Reverse DNS (rDNS) failure bounces from AT&T (ATT) occur due to ATT using rDNS records as a key signal for determining email reputation and whether to accept or reject mail. Many systems, including ATT, check for a PTR record associated with the sending IP address; a missing or mismatched record will result in failures. Initial tests by some experts indicated no issues, suggesting the failures can be localized. Properly configuring reverse DNS, ensuring a match with forward records, and contacting ATT are crucial steps to address these failures.
Key opinions
- rDNS and Reputation: Reverse DNS is a crucial element of email reputation, influencing AT&T's acceptance decisions.
- PTR Record Importance: Many systems, including AT&T, check for PTR records, and their absence can lead to rejections.
- Potential Localization: rDNS issues can sometimes be localized to specific ESPs or parts of an ESP.
- rDNS Configuration: Properly configured rDNS that matches forward records is essential for AT&T acceptance.
Key considerations
- rDNS Setup: Ensure that reverse DNS is properly configured for your sending IP address.
- Forward/Reverse Match: Verify that your reverse DNS records match your forward DNS records.
- Contact ATT: If issues persist despite proper configuration, reach out to AT&T for further assistance.
- Localized Issues: Check if the issue is specific to your ESP or a subset of their infrastructure.
Expert view
Expert from Word to the Wise responds that it is imperative to make sure that your reverse DNS is properly set up and matches forward records to avoid getting rejected by ATT.
12 Nov 2022 - Word to the Wise
Expert view
Expert from Spam Resource explains that many systems check that every mail-sending IP address has a PTR record. AT&T and other ISPs often block mail without reverse DNS, so missing PTR will cause failures.
5 Mar 2023 - Spam Resource
What the documentation says
5 technical articles
Reverse DNS (rDNS) failure bounces from AT&T (ATT) are primarily caused by issues with PTR records, which map IP addresses to domain names. A missing, misconfigured, or non-matching PTR record prevents ATT from verifying the authenticity of the sending server, leading to rejections. The requirement for matching forward and reverse DNS records is crucial for strengthening sender reputation. Reverse DNS entries are stored in a special IN-ADDR.ARPA domain. Often, forward DNS A records must exist before PTR records can be properly set up. It is important to reach out to your ISP for requirements.
Key findings
- PTR Record Mapping: Reverse DNS lookups (PTR records) resolve IP addresses to domain names.
- Authentication Failure: Missing or misconfigured rDNS records prevent AT&T from authenticating sending servers.
- Matching Records: Matching forward and reverse DNS records strengthen sender reputation and help avoid filters.
- Domain Requirement: Reverse DNS entries must conform to the IN-ADDR.ARPA domain structure.
- A Record Requirement: Usually A records must exist before PTR records can be configured.
Key considerations
- Verify PTR Records: Ensure that your IP address has a correctly configured PTR record pointing to your domain.
- Ensure Records Match: Confirm that forward and reverse DNS records match to enhance sender authentication.
- Conform to IN-ADDR.ARPA: Ensure that reverse DNS records are correctly stored within the IN-ADDR.ARPA domain.
- Check Requirements with ISP: Check the requirements with your ISP around setting up PTR Records, particularly relating to A records.
Technical article
Documentation from Microsoft Learn explains that a reverse DNS lookup, or PTR record, resolves an IP address to a domain name. A failure indicates that the IP address being used doesn't have a corresponding PTR record, or the record isn't correctly configured, which can lead to email delivery issues with providers like ATT.
30 Nov 2021 - Microsoft Learn
Technical article
Documentation from Digital Ocean responds that to have the forward DNS entry and the reverse DNS entry point to the same domain, there are requirements. Usually it is that an A record needs to exist before the PTR can be setup. Check with your ISP if you are unsure of requirements.
19 Sep 2021 - Digital Ocean
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