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EDDIE3275's profile



2 Messages

Tuesday, October 29th, 2019 1:52 PM

AT&T is blocking ip address

I am not able to receive email from the IPv4 addresses and  I believe AT&T is blocking the entire /24.  The company to whom the block is currently registered recently acquired the netblock.  It was clean on all publicly viewable blacklists; can you please unblock it?


Below is the bounce they receive.  We have tried emailing abuse several times to no avail.





Delivery has failed to these recipients or groups:

Your message couldn't be delivered. Try to send it again later. If the problem continues, please contact your helpdesk.

Diagnostic information for administrators:

Generating server:

#< #5.3.0 SMTP; 553 5.3.0 flpd587 DNSBL:ATTRBL 521< >_is_blocked.For assistance forward this error to> #SMTP#

Community Support


221.4K Messages

4 years ago

We're here to help, @EDDIE3275!


If your email server was blacklisted, it may not have met the guidelines list in our Email Best Practices page. It is also recommended that your email follows all appropriate Requests for Comments (RFCs).


We also recommend checking to see if your service is blacklisted via tools like MXToolBox. If you see a block there, they have to be resolved before AT&T can assist.


The Postmaster receives numerous requests a day and are worked in the order they are received. If multiple requests are sent from one contact, it may be flagged as spam so please send just one.

Let us know if you have any further questions! Thank you for being a part of our AT&T Community, and have a great day!

Donovan, AT&T Community Specialist

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