AT&T spam blocking problem

Several of our customers have reported problems sending mail from their e-mail addresses to various addresses supported by AT&T.  We’ve identified an issue sending to e-mail ending in the following domains:

Other domains hosted by AT&T, such as and, are unaffected.


When you send a message, you receive an immediate rejection e-mail back stating that it did not go through, and the diagnostic code provided in that message looks like the following:

<>: host[] said: 553 5.3.0 alph133 DNSBL:RBL 521<
_is_blocked.__For_information_see_ (in reply to MAIL FROM command)


Unfortunately, the server which handles e-mail has chosen on their end to block messages from our outbound mail server. We have repeatedly notified AT&T of this problem. They have refused to address it and claim that this blocking is not occurring despite the evidence we continue to send them.

At this point if you need to send messages to an email address ending in we have two workarounds to offer:

1) Ask that friend/client for an alternate e-mail address, and send your message to them at that alternate address. No other ISPs are blocking us, and you can send to all addresses except for the ones that AT&T is blocking.

2) Log in to your e-mail account via our website at You can click on “Compose” inside web mail to create a message, and copy and paste the e-mail you want to send into that web screen. Our webmail interface passes through a different server that AT&T is not blocking.

At this time, because the blocking is occurring on their end and the final resolution is in AT&T’s hands, we do not anticipate a fix on any sort of reasonable timeline.  We will continue to pursue further workarounds and alternative long-term solutions.

About Bax

I'm the Technical Support Director for Spiral Internet. You can reach me during business hours at (530) 478-9822, Ext. 1. I'm happy to answer your questions!
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