AT&T, Bellsouth and SBC deliverability best practices

AT&T, Bellsouth, and SBC use the Yahoo! email infrastructure to filter messages. The receiving Mail Transfer Agent (MTA) is located within AT&T's network. Messages accepted at the gateway by AT&T servers are relayed to the Yahoo! anti-spam filters, and displayed within the AT&T webmail platform. 

Follow AT&T and Yahoo’s best practices to help improve your chances of reaching the inbox. 

 Best Practices 

  • Ensure your email program follows all applicable spam laws and is CAN-SPAM compliant.
  • Ensure all sending IP addresses have a valid, non-generic reverse DNS (PTR) record.
  • Do not send email from a dynamic IP address.
  • Use a reputable sending system to send email such as from an Email Service Provider (ESP) or Mail Transfer Agent (MTA) software. Many home and office computers unknowingly send spam (spam zombie) after being infected with malware. Sending bulk email from a home or office email system is perceived to be spam by AT&T.
  • Do not send AT&T large volumes of email all at once. Send smaller volumes of email over longer periods of time so you do not appear like a spammer.
  • Use opt-in permission methods and have a list hygiene process in place to avoid your sending IP address from being placed on a blacklist.
  • Use consistent from domains and addresses. Changing domains and sending addresses often gives the appearance you are trying to game the system and send spam.
  • Use Sender Policy Framework (SPF), Domainkeys Identified Mail (DKIM), and Domain-based Authentication, Reporting, and Conformance (DMARC) for all email.
  • Respect AT&Ts server resources. Do not attempt too many concurrent simultaneous connections or try to send to a large number of AT&T subscribers all at once. Our general recommendation is 5 concurrent simultaneous connections and 100 messages per connection. Monitor your bounce reports for error messages related to too many connections. Your sending reputation influences your connection and throughput levels, so you may need to adjust your settings accordingly.
  • Do not try to validate an AT&T email address by connecting to their servers but not sending an email. AT&T will block your IP address if they detect this behavior.
  • Warm up new IP addresses slowly in order to build a sending reputation. New IP addresses that are not warmed up properly will be throttled and blocked.
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