Intermittent Exchange 2007 NDR

Hello Experts:

One user is receiving errors like this from one or two senders each day. Attachments are usually involved but are small (usually under 5 MB)

System is SBS 2008, content filtering is off. SMSE 6.5 is not trapping the messages in quaratine.

The IP w.x.y.z in the error is the static IP of the SBS box.

I have checked and they are not blacklisted.

Any idea what could be causing this error ?




      Subject:    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 Sent: 13/09/2012 8:46 AM


The following recipient(s) cannot be reached:


      xxxxxxx xxxxxxxxxxx on 13/09/2012 9:01 AM

            The e-mail account does not exist at the organization this message was sent to.  Check the e-mail address, or contact the recipient directly to find out the correct address.

            <xxxxxxxxxxxxxxxxxxxx #5.1.1 smtp;550 5.1.1 Relay denied for xxxxxxxxxxxxxxxx via w.x.y.z>
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Brett4567Author Commented:
Found out the problem - Exchange back pressure.

C:\ on the server was down to 1.8 GB free space. Once I moved WSUS email started flowing again.

The clue was an "insufficient resources" error when emailing via telnet.

The "relay denied" error was a red herring resulting from sending to the next highest priority MX record
WORKS2011Austin Tech CompanyCommented:
Make sure the users cached contact list does not have any misspelled email addresses, if so delete from suggested contacts.
Simon Butler (Sembee)ConsultantCommented:
The error means what it says.
What it does NOT mean is that the email is being delivered to the correct server.

Is this for inbound or outbound email? If it is inbound email, do you have more than one server listed in your MX records?

Brett4567Author Commented:
Points to Simon as he got me on the right track
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