AT&T & Yahoo - Your customers are not receiving their email - 5.3.0 flph384 DNSBL RBL 521

popowich

EQ Forum Admin
Staff member
Dear AT&T,

The customers of some large email service providers can not send email to the users in your acquired domains such as snet.net, prodigy.net, and ameritech.net, at least some of which may have been outsourced to Yahoo.

An example log file is 553 5.3.0 flph384 DNSBL:RBL 521 < x.x.x.x > is blocked.

The technical support representatives at 1-888-803-2455 insist that the problem is, and that it is correct, that you are blocking email from senders when the MX record for their domain points to a different IP address than the IP address of their SMTP relay servers.

It's mind boggling that this is really a check a large email service provider could be performing.

I hope this response is a misunderstanding, but it has been told to your customers several times who can not receive email from other ISP's.

Please do not put the blame on other ISP's when you appear to be blocking email for a technically incorrect reason.

The online form for AT&T delisting requests insists the above SMTP relay is not blocked.

I suspect the real issue may be that the internal RBL used within the AT&T servers is not updating for the the acquired domain names mentioned above.

I have an escalation open with abuse_rbl@abuse-att.net that is awaiting a response.

It is not clear if it is AT&T, Yahoo, or some other outsourced support is behind the scenes providing support to resolve this issue.

I would appreciate if someone from AT&T who understands the nature of this problem and can help address this issue would contact me for more information.
 

ryanlath

New Email
I believe I'm having a similar problem with .pacbell.net domains from my servers. How did you explain it to att to get to them to understand?

Example:
553 5.3.0 alph137 DNSBL:ATTRBL 521< x.x.x.x >_is_blocked.__For_information_see_http://att.net/blocks

Thanks,
Ryan
 

popowich

EQ Forum Admin
Staff member
Hi Ryan,

I explained it to abuse_rbl@abuse-att.net that even though att.net addresses were receiving OK, their legacy email services such as Prodigy were rejecting the email.

Double check the sender score of your IP address before opening a ticket to verify the world thinks your reputation is OK.

:welcome: to Email Questions!
 

eLIANT

New Email
Is this happening again? I have a score of 84, and I am not listed on any blocklists. But my web clients can't communicate w/ ATT.NET or Prodigy users.

Same outbound bounce:
playenviro@ameritech.net
SMTP error from remote mail server after MAIL
FROM:<mike@playcareservice.com>:
host ff-ip4-mx-vip1.prodigy.net [144.160.159.21]:
553 5.3.0 flph392 DNSBL:ATTRBL 521< 142.4.18.43>
_is_blocked.__For_information_see_http://att.net/blocks
 

franky303

New Email
They have checked and unblocked our IP within a couple of hours! They had multiple spam incidents from the IP range from our ISP, so we were unlucky and also got blocked being part of that IP range with our server. After checking our specific IP, we got whitelisted.
 

Chris Truitt

New Email
Take a look at AT&T's error message page. AT&T
The bounce back containing 521 indicates 'The sending system has been identified as a source of spam.' Thus you got too many spam complaints or your sending I.P. may be blacklisted.
 

popowich

EQ Forum Admin
Staff member
Hi Chris,

Yes, a reputation problem such as too much spam is typically the problem with these types of error messages.

For this specific problem, it was a problem with AT&T. Their RBL updates were not being pushed to legacy acquisitions such as Prodigy. Good senders were unintentionally being blocked by AT&T.

The result was that after an unblock request was processed it would be possible to email the primary AT&T email hosting, but not other domains they host such as the old Prodigy domain.
 

Chris Truitt

New Email
Thanks Popowich. That's interesting. My sender is on a private IP which is not listed with any of blacklists. I'll keep an eye out for this.

Thanks.
 

popowich

EQ Forum Admin
Staff member
I'll clarify that others might have had real spam issues in this discussion, but the problem & solution related to the original post that I made was the error found and fixed within AT&T.

Are you currently blocked? What's the sender score for the mail server you're supporting that can't send?
 

Mike Stroven

New Email
AT&T and it's sub-companies have been doing this for years! I have repeatedly (every 3-6 months) had to fill out their stupid online form saying that my stuff is being blocked, and asking them to stop blocking. They usually do (eventually) unblock me, only to autoblock me a few months later. I have a subscription to mxtoolbox which checks hundreds of blacklist servers on the web every day to make sure that my mail server is NOT LISTED. Yet AT&T blocks me anyway. It's a load of crap!
 
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