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ph6399's profile



1 Message

Tue, Jan 9, 2018 5:29 PM

550 5.7.1 Connections not accepted from servers without a valid sender domain.


We are getting Remote Server returned ' ' for many emails sent to ATT email servers (,,, etc).  Online Tools verify that our reverse lookup is correct.  Any recommendations to resolve?


Example NDR:

NDR.PNG Reverse Lookup:


2 Attachments

Community Support


2.6K Messages

4 y ago

Hi @ph6399,


I am sorry about the issues you are having with the E-mails being blocked, but I will be glad to help. Please send us an E-mail to


David, AT&T Community Specialist



2 Messages

4 y ago

We're getting the exact same error and emails sent to have gone unanswered for nearly a week.  Followup emails only result in an autoresponder with new ticket numbers.


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