Exchange 2007 NDR - Non-delivery Reports

Microsoft Exchange 2007 NDRs (Non-delivery Reports)

Let us suppose that Outlook sends an email to recipient on an Exchange 2007 server, however, that server calculates that it cannot deliver the message - what happens next?  The answer is the 'Generating Server' sends a NDR (Non-delivery Report) back to the sender's Outlook.

At first, it comes as a revelation when you discover that there is more than one type of Exchange 2007 NDR.  Then you discover that NDRs have enhanced status codes.  Furthermore, each code number gives you extra information about the cause of the email delivery problem.  This page will help you troubleshoot these NDR codes.

Topics for Exchange 2007 NDRs (Non-delivery reports)

• Interpreting Your NDR in Exchange
• NDR (Non-delivery Report) Example
• List of Exchange 2007 NDR Codes and their Meanings
• Tools and Tips for Troubleshooting Exchange NDRs
• Settings to Enable or Disable NDR Exchange 2007
• Summary - Exchange 2007 NDRs

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Interpreting Your Exchange NDR

Diagnostic Information for Administrators

When you examine the diagnostic information in a NDR message, make a note of the three-digit code, for example, 5.3.1.  In Exchange 2007, these are know as 'Common Enhanced Status Codes'. 

If the first number begins with 5, then it means you are dealing with a permanent error; this message will never be delivered.  Occasionally, you get an Exchange NDR beginning with 4, in which case there is hope that email will eventually get through.  The place to look for this NDR status code is on the last line of the report.

NDR codes such as 5.5.0, or 4.3.1, may remind you of SMTP errors 550 and 431.  Indeed, the 500 series in SMTP has a similar meaning to the 5.y.z codes in an NDR - failure.  Perhaps you have worked out why there are no 2.y.z Exchange NDRs?  The reason being the 2.y.z series mean success, whereas Non-delivery Reports, by definition, are all failures.

NDR Classification for Common Enhanced Status Codes
Clearly these status codes are not random numbers, thus we can detect patterns.  The first number 4.y.z, or 5.y.z refers to the class of code, for example, 5.y.z is permanent error.  Incidentally, I have not seen any status codes beginning with 1.y.z, 3.y.z, or have I seen any numbers greater than 5.7.z.

The second number x.1.z means subject.  This second digit, 1 in the previous example, gives generic information, whereas the third digit (z) gives detail.  Unfortunately, I have not cracked the complete code for the second digit.  However, I have discovered a few useful patterns, for instance, 5.1.x indicates a problem with the email address, as apposed to server or connector problem.  In addition, 5.2.x means that the email is too big, therefore I recommend checking the message limit setting on the Exchange 2007 server.

Conclusion, research the three-digit error in your enhanced status code, see Exchange NDR codes below.

NDR (Non-delivery Report) Example

Here below is an example of an email sent to a non-existent user.  There is no jethro mailbox on the worcester server.  In the body of the NDR, you can see the name of the domain (exchJethro.com), the server (worcester) and the NDR status code (5.1.1).  In your examples, always seek out the servername in the Received: from server (IP Address) of your NDR.

List of Exchange 2007 NDR Codes and their Meanings

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Tools and Tips for Troubleshooting Exchange NDRs

Exchange Mail Flow Tools
1) Launch the Exchange Management Console
2) Click on the Toolbox
3) Examine the Mail flow Tools

Alternatively:
Download the Microsoft Exchange Troubleshooting Assistant v1.1, one of its components is the Exchange Mail Flow Troubleshooter.  Here are some of the problems where it can help you:

• Emails are delayed, or are not received.
• Users receive NDRs which are difficult to interpret.
• Messages are accumulating in one of the queues on the Exchange 2007 server.

Mail Flow Troubleshooter will diagnoses the retrieved data, and even make suggestions for cures to your NDR problems.  You enter the symptoms from a pick list, the Mail Flow Troubleshooter then employs built-in logic to suggestion solutions.

ExBPA (Exchange Best Practice Analyzer)
It may be a help, or the ExBPA may distract you from troubleshooting NDRs.  What the ExBPA will do is provide a general health check for the Exchange 2007 server.

Check the Logs
Good technique is to begin by looking in the Application log for errors.  A variation of this tip is to increase the Diagnostic Logging.

Check the queue and SMTP logs on the Exchange 2007 server.

Firewalls and Anti-virus software
You may try turning off temporarily anti-virus software and even the client-side firewall to see if that enables the email to get through.

PowerShell for Viewing Queues
It may speed up troubleshooting your Exchange NDR if you use the PowerShell cmdlets, for example:
get-Queue <QueueId>
retry-Queue <xyz>
get-Message -queue <QueueID>

Note: Each cmdlet has switches or parameters, try: get-Help verb-noun to find out more about an interesting cmdlet.

Regtrace
You could also gather more clues about your Exchange NDR with Regtrace, which you find on the Exchange 2003 CD in the support\utils\i386 folder.  Regtrace gives you detailed information e.g. homeMDB =
CN=Mailbox Store (JethroMail-Managers),CN=First Storage Group,CN=InformationStore,CN=JethroMail-Managers,CN=Servers,CN=First Administrative Group,CN=Administrative Groups,CN=First Organization,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=JethroMail,DC=com

Telnet
Try telnet over port 25.  Naturally, you need to substitute a real Exchange 2007 server for 'YourServer'.  Open a command prompt, type:

Telnet YourServer 25

Success means that the SMTP mail server is available.  See here for help with Telnet troubleshooting.

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General Troubleshooting Advice for Exchange NDRs

One of the best approaches to troubleshooting is to keep asking questions until you isolate the problem.  In the case of an NDR, discover if the fault lies with the Exchange 2007 server itself, the sender, or the recipient.  Here are ways of collecting more clues;

• Send another email to the same recipient but using a different sender.
• If it's attachment, then try with no attachment.
• If it's just one email address that produces the Non-delivery report, what happens if you type the SMTP address manually, compared with when you click the user account in the GAL?
• Alternatively, you could send emails to different recipients from the original sender. 
• Is the the Exchange NDR random, or can you reproduce it easily?
• Do you have multiple sites?  If so are they all affected, or just one?
• If all else fails try sending an email to oneself! 
• Bear in mind that Microsoft Outlook has a 'Test Account Settings' button to collect information from the client side.
• Check the logs (mentioned in the tools section).

My favoured non-delivery troubleshooting technique is to narrow the search area to a particular server, mailstore or Routing Group Connector?  However, if that fails then I would expand the search area by sending email to different sites, or to internet users. 

I was initially annoyed because one particular ISP would only troubleshoot NDRs if I used the Outlook Express client.  At first I was annoyed, but then I realized that you get different responses from different email clients.  Therefore my tip is, try a different version of Microsoft Outlook.

Settings to Enable or Disable NDR Exchange 2007

It is possible to disable NDR in Exchange.  However, there is more then one place to visit if you want to turn off NDRs in Exchange 2007 server.  Log on as administrator, and navigate to the Exchange Management Console.  It makes most sense to start with the Hub Transport node, remember this role is needed if you send emails to recipients on the same server.

Disable NDR Exchange 2007 Hub Server

• Launch the Exchange Management Console
• Expand the Organization Configuration folder
• Click on Hub Transport
• Select Remote Domains (Key point)
• Right-click Default (Tab)
• Click on the Message Format (Tab)
• To turn off NDR, remove the tick on Allow non-delivery reports.  (See NDR screenshot to the right)

Note:  You can also control 'Allow delivery reports' on this tab.  These are the normal DSN delivery status notifications.

PowerShell commands to disable NDR in Exchange 2007

If you are experimenting with allowing, or disabling NDRs, then this PowerShell cmdlet will be quicker.

Launch the Exchange Management Shell type:

Note 1:  "Default" is the name of the Remote Domain setting where you want to turn off NDR.

Note 2:  To Allow non-delivery reports, change
set-RemoteDomain "Default" -NdrEnabled $false
to
set-RemoteDomain "Default" -NdrEnabled $true.  This places a tick in the checkbox.  If you clear this option, NDRs aren't sent to any email address in the remote domain.

Note 3:   For more information about this, or any other PowerShell cmdlet, precede the command with get-Help.  For example: get-Help set-RemoteDomain.

Turn off NDR Exchange 2007 for Unified Messaging Role

This ability to control NDRs is particularly useful on servers with the Unified Messaging Role.

• Launch the Exchange Management Console
• In the left tree, expand the Organization Configuration node
• Click the Unified Messaging folder.
• On the UM Dial Plans tab, select the UM dial plan that you want to manage, and then select Properties.
• From the General tab, check or clear the box next to 'Send a non-delivery report if message delivery fails'.

There several reasons to turn off NDR in Exchange 2007; for example, virus infections, spam infiltration or spoof attacks.

Note: there is no Badmail folder option in Exchange 2007, not even a registry hack.  Instead badmail remains in the pickup folder, you will spit the badmail by the .bad file extension.

Exchange Server 2007 is a complex topic, do you need practical hands on training?  As an MCT trainer, I can thoroughly recommend TrainSignal.  In particular, I like the way that TrainSignal cover all learning methods, instructor lead, video and of course text material.  You can either take one module, for example Exchange 2007 or go for a combination of modules.  Learn more about Microsoft Exchange Server 2007 here

See more Microsoft Exchange Server 2007 topics:

• Exchange 2007 Home   • SP1   • Migration   • Compatibility   • ExBPA   • Free Syslog Analyser

• Install   • Server Roles   • CAS Role   • Hub Transport  • SMTP Connector   • NDRs  • Exchange CCR

• Mailbox Role   • Create Mailbox   • Mailbox Stores   • Recipients   • OWA   • GAL   • Eseutil   • Edge

Please write in if you see errors of any kind.  Please report any factual mistakes, grammatical errors or broken links, I will be happy to not only to correct the fault, but also to give you credit.

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