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Exchange: Sent messages bounce back

Posted on 2008-06-13
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Last Modified: 2010-04-18
Anybody familiar with a problem like this?:
When we email someone in the Bellsouth domain, we get this bounce back:
Running SBS 2003
From:   System Administrator  
Sent:   Friday, June 13, 2008 8:35 AM
To:     Sandra User
Subject:        Undeliverable: Todays topic
Your message did not reach some or all of the intended recipients.
      Subject:   Undeliverable: Todays topic
      Sent:     6/13/2008 8:35 AM
The following recipient(s) could not be reached:
      someone@bellsouth.net on 6/13/2008 8:35 AM
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            <host.iccbuild.com #5.5.0 smtp;550-68.213.237.115 blocked by ldap:ou=rblmx,dc=att,dc=net>
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Question by:HardwareDude
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4 Comments
 
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Expert Comment

by:Dovinshka
ID: 21780085
From that information, you are listed on a an RBL blacklist.

However in saying that, your IP is not listed here - http://www.mxtoolbox.com/blacklists.aspx

Have you got a reverse DNS record set?

Dov.
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Assisted Solution

by:Dovinshka
Dovinshka earned 200 total points
ID: 21780127
It appears as though you do have a reverse DNS record.

You will have to submit a ticket to ATT to remove their entry. You can do that here - http://worldnet.att.net/general-info/mail_info/block_inquiry.html

Dov.
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LVL 58

Accepted Solution

by:
tigermatt earned 800 total points
ID: 21780132
According to the NDR your server's IP has been added to an RBL (real time blacklist) at AT&T and you have therefore been blocked from sending to Bellsouth. You will also have been blocked from sending to other servers and mail systems which implement the same RBL.

There are several reasons for being added to an RBL. These may include: sending mass, unsolicited spam; being an open relay; not having correct DNS settings and the list goes on.

I would first start by checking you are not an open relay, as per the instructions at http://www.amset.info/exchange/spam-cleanup.asp. If that test is clean and shows no faults, the other possibility is DNS configuration. You must read this guide carefully and check everything described in each section is correctly set: http://www.amset.info/exchange/dnsconfig.asp.

I would also be thinking about whether there may be some spam-bot on your network which is mass-mailing - using its own built-in SMTP engine (they seldom use a local mail server) - spam using your IP. That would get you blocked. You can stop this by configuring your firewall to only allow the IP address of the Exchange Server to connect outbound to the Internet on port 25. That doesn't rule out a spam-bot on the server though.

One of the easy options which you might be able to use is to configure a Smart Host in the mean time. This will allow you to send mail through an SMTP server provided by your ISP or website hosting company to send mail through, and will usually a) stop you getting blacklisted and b) make it easier to send mail all over the place in the future. The ISP systems are much bigger and configured to handle all these sorts of things.

-tigermatt
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LVL 58

Expert Comment

by:tigermatt
ID: 21780143
As per the article posted above, you can request AT&T remove your entry, but if you don't put right the issues I've already mentioned, you will quickly find yourself back on at least that RBL, and potentially many others in the future.
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