Email provider
AT&T SMTP Error Codes and Bounce Messages
AT&T operates mail for att.net, sbcglobal.net, bellsouth.net and related legacy domains. It runs a postmaster site with a route for disputing spam verdicts.
- Codes on record
- 1
- Responses
- 3
- Domains
- att.net, sbcglobal.net, swbell.net, bellsouth.net
SMTP 5503 responses
smtp;550 5.2.1 <[email protected]>... Addressee unknown, relay=[x.xx.xx.xx]
smtp;550 5.2.1 <[email protected]>... blank mailhost - invalid address, relay=[x.xx.xx.xx]
smtp;550 5.7.1 Connections not accepted from servers without a valid sender domain. ## Fix reverse DNS for x.xx.xx.xx
A hard failure. The receiving server has refused the message for good and will not accept an unchanged retry without a change on the sending side. See SMTP 550 across every provider
AT&T bounce questions
›Why is AT&T bouncing my email?
AT&T operates mail for att.net, sbcglobal.net, bellsouth.net and related legacy domains. It runs a postmaster site with a route for disputing spam verdicts. Match the exact wording of your bounce to one of the 3 responses on this page to find the specific reason and fix.
›How do I improve deliverability to AT&T?
Authenticate with SPF, DKIM and DMARC, keep your sending IP and domain reputation clean, mail only engaged recipients, and honour unsubscribes. AT&T also publishes postmaster guidance, linked on this page.
