Email being blocked by AT&T

Email being blocked by AT&T with the following:

There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            < #5.5.0 smtp;550- blocked by ldap:ou=rblmx,dc=att,dc=net

Exchange 2003  - the SMTP Diagnostics from MXtoolbox shows "This server is not an open relay"

Just started on 6-12-2008 - BellSouth recently bought by A T & T hasn't happened for years - need to fix ASAP - How to get them (AT&T) to stop blocking my email
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Hypercat (Deb)Connect With a Mentor Commented:
You need to go to their website and fill out the request form to have them remove whatever they have that is blocking you.  I just had this happen to one of my clients too. I think this link will take you to the right web page to send this request:

Choose the "Tools for Administrators...." link.
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