NDR - # 5.3.0 smtp; 553 5.3.0

my ussers cannot deliver to sbcglobal.net or prodigy.net

NDR generated to recipients saying..

Your message did not reach some or all of the intended recipients.
Subject:  blank
Sent: date & time
The following recipient(s) cannot be reached:
user@sbcglobal.ent on such date & time

The message cannot be delivered due to a configuration error on the server.
Please contact your Administrator

<mydomain  #5.3.0 smtp; 553 5.3.0 flpi095 - m99l6vr30128001, DNSBL :521< >_blocked. _For information_see_http://att.net/blocks >

when checking this code with att.net.. I did not see the match. Please help.

We only filter incoming mails. .
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BertlingConnect With a Mentor Commented:
look like your on a spam blacklist.
please check you RDNS records at www.mxtoolbox.com

also read this and make sure it applys correct to your server: http://www.amset.info/exchange/dnsconfig.asp
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