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5.5.0 smtp: 550 blocked by ATT.NET

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5.5.0 smtp: 550 blocked by ATT.NET - 4.May2007 3:48:33 PM   


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Joined: 24.Apr.2007
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Exchange 2003 Sp2 Standard with a vanilla install (no SMTP Connectors). We have begun to have issues with emailing an ATT.NET associate. We'll send an email and get

There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
           <gsi-fs2.MYDOMAIN.com #5.5.0 smtp;550- blocked by ldap:ou=rblmx,dc=worldnet,dc=att,dc=net>

Based on DNSTUFF, our DNS records appear fine (we could use an SPF record). I also checked against blacklists, and again we appear fine.
When I google
"#5.5.0 smtp;550-" "blocked by"ATT.NET
it seems to be not an uncommon problem based of forum threads, but none ever show resolution. It seems to be an issue of ATT.NET being aggressive with its SPAM filtering and forwhatever reason we are caught in it.

I am not sure there is much we can do, other than educate our partner for them to contact and correct with ATT.NET?

I did see a somewhat similar thread at microsoft communities:
which focused on adding an SMTP Connector, but its focus was on small business server.

Wondered if any others experienced similar situations? Thanks, Dan
Post #: 1

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