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Not sure what these messages are:

Posted on 2006-11-22
Medium Priority
Last Modified: 2010-03-06

Our clients are receiving a number of NDR's for ficticious names BUT the correct domain names.

Below is an example of the error from the daily performance report.

Source                          Event ID    Last Occurrence     Total     Occurrences
MSExchangeTransport    7010         22/11/2006           04:14    35 *
This is an SMTP protocol log for virtual server ID 1, connection #106. The client at "" sent a "helo" command, and the SMTP server responded with "501 5.5.4 Invalid Address ". The full command sent was "helo |". This will probably cause the connection to fail. For more information, click  
We did setup some monitoring on this server because we thought they were an open relay - but can remember where we set-up the monitoring or even if these NDR's are a result of that monitoring.

Either way, are these NDR's normal - is there a problem and can it be fixed????

Many thanks
Question by:AndyKeen
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Expert Comment

ID: 17998278
Can you post the contents of one of the NDR messages and how many they are getting?

My first inclination is simply to say they are generated by spammers who are attempting to send messages to users on that server using a from address in the same domain. It is a fairly common practice.
Message from:
Message to:

Another possibility is that they are the victim of a Joe Job--a spammer using one of their email addresses in the from line. In that scenario, though, the number of NDRs generated is a much higher volume.

Recently I have even seen fake NDRs generated as the spam--it looks like it was sent from me to someone else and their mail server rejected it. Scrutiny of the header shows that it was not an NDR generated from an actual bounce.

Author Comment

ID: 17998421
Hi Susan - Thanks for your info.

Below are two typical NDR's - note that the domain names are correct but the pre- @ is incorrect.

Your message did not reach some or all of the intended recipients.

      Subject:      Irene Deutsch/ALBD/HeavyStamping ist in Karenz
      Sent:      22/11/2006 15:02

The following recipient(s) could not be reached: on 22/11/2006 15:07
            The message contains a content type that is not supported
            < #5.6.1 smtp;554 5.6.1 Body type not supported by Remote Host>

E.G. 2

Your message did not reach some or all of the intended recipients.

      Subject:      somewhat daily
      Sent:      21/11/2006 16:33

The following recipient(s) could not be reached: on 21/11/2006 18:07
            A configuration error in the e-mail system caused the message to bounce between two servers or to be forwarded between two recipients.  Contact your administrator.
            < #4.4.6>

Note - the domain name  (Changed) is a valid domain name as is (Changed) - the pre - @ is a valid name but more luck than judgement perhaps.

Hope this helps.


Accepted Solution

susanzeigler earned 2000 total points
ID: 17999492
From the way you stated, it sounds like the from address in the original message that generated the NDR was valid and on the local server. Just to be safe, the next thing I would do would be to check the serverlog files to see if the messages shown in the NDR originated on the server or even passed through it. Sometimes a spam will hit the server, then be rejected, and then the NDR on the spam message generates another NDR because the original sending address wasn't valid (boy I hope that made sense).

One possibility is that there is a compromised computer on the network. More likely, it is just spam, but it is better to be careful.

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