Why am I seeing reverse DNS failure bounces from ATT?
Matthew Whittaker
Co-founder & CTO, Suped
Published 16 Apr 2025
Updated 13 Oct 2025
7 min read
Suddenly seeing a wave of reverse DNS (rDNS) failure bounces specifically from AT&T email addresses can be a perplexing and frustrating experience for any email sender. It implies that your meticulously crafted emails, despite appearing to be correctly configured, are being rejected before they even reach the recipient's inbox.
This type of bounce message, often accompanied by error codes indicating a DNS lookup failure, suggests that AT&T's mail servers are having trouble verifying the authenticity of your sending IP address. While sometimes it points to an actual misconfiguration on your end, many senders report these as false positives or temporary glitches originating from AT&T’s infrastructure itself.
Understanding the root cause is crucial to resolving these bounces and maintaining your email deliverability. Here, I'll explore what rDNS is, why AT&T relies on it, the common reasons for these failures, and what steps you can take to diagnose and mitigate the problem.
What is reverse DNS and why is it important for email?
Reverse DNS, or rDNS, is a method of resolving an IP address back to its corresponding domain name. Think of it as the opposite of a standard DNS lookup, which translates a domain name into an IP address. For email, rDNS relies on Pointer (PTR) records configured by your internet service provider (ISP) or hosting provider for your sending IP address.
Mail servers, including those operated by AT&T, commonly use rDNS as an anti-spam measure. When an email server receives an incoming connection, it performs an rDNS lookup on the sending IP address. If the IP address does not have a valid PTR record, or if that record does not align with the sending domain, the receiving server might flag the email as suspicious, potentially blocking it or sending it directly to the spam folder. This is a fundamental part of the overall email authentication process, alongside SPF, DKIM, and DMARC.
Therefore, a reverse DNS failure bounce means that AT&T’s mail server could not successfully perform this check, perceiving your sending server as unverified or potentially malicious. This often results in bounce messages like 550 5.7.1 Connections not accepted from servers without a valid sender domain.
Understanding PTR records
Purpose: PTR records map an IP address to a domain name, verifying that the IP address is authorized to send email from that domain.
Spam Prevention: Many recipient mail servers require valid rDNS as a basic check to filter out spam and malicious emails. Without it, your emails are more likely to be considered suspicious.
Why you might be seeing these bounces
There are primarily two categories of reasons why you might be seeing reverse DNS failure bounces from AT&T. The first relates to your own email sending infrastructure and its configuration. This is often the easiest to identify and fix. Common issues include a missing PTR record, an incorrectly configured PTR record that doesn't match your sending domain, or a mismatch between your SMTP banner and your rDNS record, which can lead to your domain being blacklisted (or blocklisted).
The second category, which can be more frustrating because it's outside your direct control, involves transient or systemic issues on AT&T’s side. Sometimes, their mail servers might experience temporary glitches or lookup failures that cause legitimate emails to bounce. This can manifest as intermittent high bounce rates for AT&T, SBCGlobal.net, and Bellsouth.net domains.
When AT&T’s systems encounter a lookup issue, whether it’s a legitimate misconfiguration on your part or a temporary network hiccup on theirs, you'll typically receive a bounce message. A common one is the 550 5.7.1 error code indicating that connections are not accepted from servers without a valid sender domain. This particular error often points directly to an rDNS (PTR) issue, though it can sometimes be a false positive due to AT&T’s own lookup failures.
Your sender issues
Missing PTR record: Your sending IP address lacks a PTR record mapping it to your domain.
Mismatched PTR: The PTR record exists, but it resolves to a different domain than the one you are sending from, or it doesn't match your SMTP banner (EHLO/HELO command).
DNS propagation delays: You recently updated your PTR record, and AT&T's DNS resolvers haven't caught up yet.
AT&T network issues
Temporary glitches: AT&T’s DNS resolvers may experience intermittent issues, leading to failed lookups for otherwise valid PTR records.
Network specific blocks: Certain AT&T network nodes might temporarily block traffic from specific IP ranges, erroneously citing rDNS failure.
Maintenance/Updates: During system maintenance or updates, their DNS resolution services might be temporarily impacted, resulting in increased email bounces.
How to diagnose and resolve AT&T rDNS failures
When encountering reverse DNS failure bounces from AT&T, the first step is always to verify your own configuration. Use a reliable reverse DNS lookup tool to check if your sending IP address correctly resolves back to your domain. You should also ensure that your SMTP server's banner (the HELO/EHLO name) matches your PTR record. Any discrepancies here can trigger rejections from vigilant mail servers. This is a crucial step in preventing PTR record related bounces from major ISPs like Google as well.
If your PTR record and SMTP banner are correctly configured and have been stable for a while, the issue might be on AT&T’s side. In such cases, the problem is often localized to specific AT&T network nodes or is a temporary system anomaly. While you can't directly fix their infrastructure, monitoring the situation and contacting AT&T’s postmaster team or your own email service provider (ESP) can help.
Example: Reverse DNS lookup using digBASH
dig -x 192.0.2.1 +short
When dealing with persistent issues, especially those causing a significant percentage of your AT&T traffic to fail, consider implementing robust email monitoring. This includes checking your domain's reputation, maintaining proper email authentication (SPF, DKIM, DMARC), and keeping an eye on bounce logs for specific error messages. Being proactive can help you identify and react quickly to unexpected deliverability issues, whether they stem from your setup or external factors like an ISP’s temporary blocklist (or blacklist).
For ongoing deliverability success, a holistic approach is key. Regularly review your DNS records, ensure your sender reputation is healthy, and be prepared to troubleshoot if you notice a sudden increase in bounces from any major mailbox provider. Sometimes, patience is also a virtue, as temporary glitches on the recipient side often resolve themselves, but it's always best to rule out your own configuration first. You can also refer to guides on sudden increases in DNS failure bounces for broader troubleshooting advice.
Step
Action
Details
1
Verify PTR record
Use a PTR lookup tool to confirm your sending IP maps to your domain.
2
Check SMTP banner
Ensure your mail server's HELO/EHLO name matches your PTR record.
3
Monitor bounce logs
Look for specific error codes like 550 5.7.1 and track bounce rates to AT&T.
4
Contact support
If your setup is correct, reach out to your ESP or AT&T’s postmaster team.
Moving forward with confidence
Dealing with reverse DNS issues, especially with large mailbox providers like AT&T, can be tricky. My experience tells me that while sometimes it’s a clear misconfiguration on the sender’s side, other times it’s an elusive glitch in the recipient’s system. Staying informed and connected within the email community is invaluable for quickly identifying widespread issues and knowing when to escalate.
Even when a problem seems to be external, understanding your own setup is paramount. Always confirm your DNS records, including PTR, are correctly published and propagated. This foundational work will save you countless hours of troubleshooting when unexpected bounces occur. It’s also important to remember that some issues resolve on their own, but active monitoring (or keeping up with deliverability trends) helps differentiate a transient issue from a persistent problem.
The key to good email deliverability, especially when facing issues like rDNS failures, is a combination of meticulous setup, vigilant monitoring, and timely communication with your service providers or even the recipient ISP. Don't assume anything, test everything, and when in doubt, reach out to the relevant support channels. This proactive stance ensures your emails have the best chance of reaching the inbox.
Views from the trenches
Best practices
Maintain correct PTR records for all sending IPs and ensure they match your SMTP banner.
Regularly monitor your email logs for unusual bounce patterns, especially those from major ISPs.
Communicate proactively with your ESP or hosting provider if you suspect an rDNS issue.
Stay informed about known issues or widespread problems reported by other senders regarding major mailbox providers.
Common pitfalls
Overlooking a missing or misconfigured PTR record as the root cause of bounces.
Assuming all rDNS failures are your fault without considering transient ISP-side issues.
Not aligning your SMTP banner (HELO/EHLO) with your PTR record, leading to rejections.
Failing to track bounce rates to specific domains like AT&T, which can indicate localized problems.
Expert tips
Use multiple rDNS lookup tools for verification, as some might show cached results.
When contacting AT&T, provide specific bounce messages and timestamps to help them investigate faster.
If your ESP uses shared IPs, confirm they manage rDNS properly and notify you of any changes.
Consider a dedicated IP if you consistently face issues on shared IPs, as it gives you more control over rDNS.
Marketer view
Marketer from Email Geeks says they started seeing bogus reverse DNS failure bounces from AT&T as of that morning.
2024-07-22 - Email Geeks
Expert view
Expert from Email Geeks says that typically false positive DNS failures are localized to a single ESP or even part of an ESP and that AT&T would need to be contacted.
AT&T, commonly use rDNS as an anti-spam measure. When an email server receives an incoming connection, it performs an rDNS lookup on the sending IP address. If the IP address does not have a valid PTR record, or if that record does not align with the sending domain, the receiving server might flag the email as suspicious, potentially blocking it or sending it directly to the spam folder. This is a fundamental part of the overall email authentication process, alongside SPF, DKIM, and DMARC.
AT&T. The first relates to your own email sending infrastructure and its configuration. This is often the easiest to identify and fix. Common issues include a missing PTR record, an incorrectly configured PTR record that doesn't match your sending domain, or a mismatch between your SMTP banner and your rDNS record, which can lead to your domain being blacklisted (or blocklisted).
Google as well.
