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Why are email clients being blocked by AT&T and how was it resolved?
Summary
AT&T's email blocking issues stem from a combination of factors, including a major outage, stricter filtering practices, poor sender reputation, authentication failures, and inadequate list hygiene. AT&T uses distinct filtering methods and may be more aggressive than other ISPs. Solutions involve addressing the outage, improving email authentication (SPF, DKIM, DMARC), monitoring and acting on feedback loops and bounce rates, proper IP warming, maintaining valid rDNS records, practicing good list hygiene, monitoring data quality, and segmenting sending. Data quality and how that data is actioned is very important for keeping engagement metrics up. Correct authentication and reputation management are critical, as blocks often occur despite seemingly correct configurations.

Key findings

  • AT&T Outage: A major outage at AT&T contributed to widespread blocking.
  • Stricter Filtering: AT&T employs stricter and potentially more aggressive filtering methods.
  • Reputation Matters: Sender reputation is a key factor for deliverability to AT&T.
  • Authentication is Critical: Proper email authentication (SPF, DKIM, DMARC) is essential to avoid blocks.
  • List Hygiene: Poor list hygiene leads to higher bounce rates and complaints, affecting deliverability.
  • IP Warming Essential: Properly warming up new IPs is crucial when sending to AT&T.
  • Unique Filtering Methods: Different ISPs use different filtering methods, and AT&T may have unique rules.
  • Data Quality is Critical: Data quality and actioning upon engagement is important for list management.

Key considerations

  • Monitor Feedback: Closely monitor bounce rates and feedback loops, especially those specific to AT&T.
  • Check Reputation: Regularly check IP reputation and address blacklistings promptly.
  • Segment Sending: Consider segmenting sending to isolate problem IPs.
  • Implement Authentication: Ensure SPF, DKIM, and DMARC records are correctly configured and updated.
  • Clean Lists Regularly: Regularly remove inactive or unengaged subscribers.
  • Warm Up IPs Properly: Warm up new IPs gradually and monitor engagement.
  • Ensure Valid rDNS: Maintain a valid reverse DNS (rDNS) record.
  • Data Action: Take action against users based on engagement metrics.
What email marketers say
11 marketer opinions
AT&T experienced blocking issues due to a combination of factors, including a major outage, stricter filtering policies, and problems with sender reputation. Some marketers observed widespread blocking affecting various platforms and domains. Contributing factors included poor IP reputation (potentially due to blacklisting), authentication failures (SPF, DKIM, DMARC), and inadequate list hygiene. Resolution involved addressing the outage, improving authentication, monitoring and acting on feedback loops and bounce rates, warming up IP addresses properly, maintaining valid rDNS records, and practicing good list hygiene.

Key opinions

  • Outage: AT&T experienced a major outage that contributed to blocking issues.
  • Stricter Filtering: AT&T has implemented stricter filtering policies.
  • IP Reputation: Poor IP reputation and blacklisting can lead to AT&T blocking emails.
  • Authentication: Failure to properly authenticate emails with SPF, DKIM, and DMARC contributes to deliverability issues.
  • List Hygiene: Poor list hygiene practices result in higher bounce rates and complaints, negatively impacting deliverability.
  • IP Warming: Inadequate IP warming for new IPs is a cause.
  • rDNS Records: Invalid rDNS records can affect deliverability.
  • Dedicated IPs: Consider using dedicated IP addresses to help manage reputation.

Key considerations

  • Monitor Feedback: Closely monitor bounce rates and feedback loops specific to AT&T.
  • Check Reputation: Regularly check IP reputation using online tools and address any blacklistings promptly.
  • Segment Sending: Consider segmenting sending to isolate problem IPs.
  • Update Authentication: Ensure SPF, DKIM, and DMARC records are properly configured and up-to-date.
  • Clean Lists: Regularly remove inactive or unengaged subscribers from your email lists.
  • Warm Up IPs: Properly warm up new IP addresses before sending large volumes of email.
  • Valid rDNS: Ensure a valid reverse DNS (rDNS) record is in place for all sending IP addresses.
Marketer view
Marketer from Email Geeks shares they are seeing clients being blocked at ATT on different platforms and it started Friday. Some clients are just some IPs and some are not impacted at all.
20 Jun 2023 - Email Geeks
Marketer view
Email marketer from GetResponse advises using dedicated IPs, so the senders are not impacted by other people's bad behaviour. They advise using the dedicated IP correctly so the reputation remains high.
17 Nov 2022 - GetResponse
What the experts say
3 expert opinions
AT&T's email blocking can be attributed to its unique and potentially more aggressive filtering methods compared to other ISPs. Correct authentication (SPF, DKIM, DMARC) and a positive sender reputation are crucial, as blocks often result from failures in these areas, even with seemingly correct configurations. High data quality and good data handling processes are of utmost importance, including how data is actioned based on engagement metrics and cleaning of data.

Key opinions

  • Unique Filtering: AT&T uses distinct filtering methods which are perhaps more aggressive or stringent than those of other ISPs.
  • Authentication Importance: Proper email authentication (SPF, DKIM, DMARC) is critical for avoiding blocks.
  • Reputation Matters: Maintaining a positive sender reputation with AT&T is essential for email deliverability.
  • Data Quality Matters: Data quality and hygiene is important for good email deliverability, in terms of who you are sending to.

Key considerations

  • Review Bounce Messages: Carefully review bounce messages and feedback loops specific to AT&T to diagnose blocking issues.
  • Focus on Authentication: Prioritize correct configuration and maintenance of SPF, DKIM, and DMARC records.
  • Monitor Reputation: Actively monitor sender reputation with AT&T and take steps to address any negative trends.
  • Review engagement: Action against engagement metrics, and focus on cleaning of data
Expert view
Expert from Spam Resource emphasises the importance of correct authentication (SPF, DKIM, DMARC) and maintaining a positive sender reputation with AT&T. Blocks often arise from failing authentication or poor reputation scores, even if technical configurations seem correct.
7 Nov 2024 - Spam Resource
Expert view
Expert from Spam Resource explains that different ISPs use different filtering methods, and AT&T might be more aggressive or have unique filtering rules that trigger blocks, even if emails pass through other providers. They recommend carefully reviewing bounce messages and feedback loops specific to AT&T to diagnose the issue.
7 May 2024 - Spam Resource
What the documentation says
5 technical articles
AT&T blocks emails to protect customers from spam and malicious content using various filtering techniques. Key factors leading to blocking include high complaint rates, blacklisted IPs, and authentication failures. Maintaining a good sender reputation is critical, as AT&T, like other ISPs, uses this as a primary filter. Implementing DMARC helps verify email authenticity. Keeping SPF records up-to-date and respecting user preferences regarding unsubscribing are essential for preventing blocks. Regularly monitoring sending reputation using tools such as Google Postmaster Tools is best practice.

Key findings

  • Filtering Techniques: AT&T uses filtering techniques to protect against spam and malicious emails.
  • Complaint Rates: High complaint rates can trigger email blocking.
  • Blacklisted IPs: Sending from blacklisted IPs results in email blocks.
  • Authentication Issues: Authentication failures (SPF, DKIM, DMARC) lead to blocking.
  • Sender Reputation: Sender reputation is a key factor in determining whether to block emails.
  • DMARC Implementation: Implementing DMARC helps verify email authenticity.
  • SPF Records: Keeping SPF records up-to-date is crucial.

Key considerations

  • Monitor Reputation: Consistently monitor your sending reputation.
  • Implement Authentication: Implement SPF, DKIM, and DMARC correctly.
  • Respect Preferences: Respect user preferences regarding unsubscribing.
Technical article
Documentation from Google Bulk Sender Guidelines specifies that even though it's Google's documentation it's best practise for all ESP's to review. They recommend consistently monitor your sending reputation via Google Postmaster Tools, implement authentication (SPF, DKIM, DMARC), and respect user preferences regarding unsubscribing to prevent low reputation and therefore blocking.
15 Sep 2023 - Google Bulk Sender Guidelines
Technical article
Documentation from RFC Editor explains the importance of keeping SPF records up to date to ensure valid sources are listed. If sending practices change, the SPF records need to reflect this. Failure to do so can result in emails being blocked.
13 May 2024 - RFC-Editor.org
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