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Summary

AT&T's email filtering can be particularly stringent, leading to significant block rates, even for senders with seemingly good practices. A common issue observed is a high volume of blocks related to sending to non-existent or unengaged users. Understanding the specific SMTP bounce codes is crucial, as generic blocked messages from an ESP can hide the detailed reasons. It is vital to maintain a clean and validated mailing list to prevent such issues.

What email marketers say

Email marketers frequently encounter significant challenges with AT&T's email filtering, particularly concerning high block rates. Many suspect that these blocks are linked to emailing unengaged audiences or issues with list hygiene. The primary concern often revolves around the lack of detailed bounce messages from their ESPs, which prevents them from diagnosing and addressing the root causes effectively. This leads to a trial-and-error approach where they contact postmaster teams or seek solutions for their high bounce rates.

Marketer view

Email marketer from Email Geeks notes a 30% AT&T block rate, suspecting it relates to unengaged users (inactive for 90 days).

08 Jun 2023 - Email Geeks

Marketer view

Email marketer from Constant Contact Community reports all emails going to AT&T domains are bouncing as blocked, affecting att.net and sbcglobal.net, since December 20, 2024.

20 Dec 2024 - Constant Contact Community

What the experts say

Email deliverability experts highlight that AT&T's blocking mechanisms are sophisticated and often rely on sender reputation and list quality. They emphasize that generic blocked messages from ESPs are insufficient for diagnosis, necessitating access to full SMTP responses. The consistent message is that sending to non-existent users is a critical red flag that AT&T's systems (and often Yahoo, given their partnership) are designed to catch aggressively.

Expert view

Marcel from Email Geeks suggests that if mail is blocked at AT&T's MX servers, it most likely means they block and do not like the sender's IP addresses, and bounce messages should provide clues.

12 Jun 2023 - Email Geeks

Expert view

Expert from SpamResource warns that high bounce rates due to 'userid unknowns' are a strong signal of poor list hygiene and can severely impact sender reputation with ISPs like AT&T.

15 Mar 2024 - SpamResource

What the documentation says

Official documentation and technical reports provide valuable context for AT&T's email blocking practices. They reveal that AT&T employs robust filtering mechanisms, which can sometimes result in legitimate emails being blocked due to perceived security gaps or high spam volumes. It's also important to note the evolving nature of AT&T's email services, including changes in their email-to-text functionalities and their relationship with Yahoo, which affects mail routing and support.

Technical article

AT&T Support documentation states that firewall, antivirus programs, and anti-spyware software can cause a conflict with email programs and web browsers, leading to email issues.

01 Jan 2023 - AT&T Support

Technical article

AT&T Support documentation explains that when an email address is blocked, the AT&T Mail account automatically deletes messages sent from that account, so the user never sees them.

01 Jan 2023 - AT&T Support

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