Exchange Not Delivering NDR to Outside Addresses

Posted on 2006-03-21
Last Modified: 2012-06-27
This question is slightly involved as it incorporates our proprietary software developed by my company, I will explain the best I can.

We have a Newsletter service for Real Estate agents.

Our application masks the From field to match that of the users Personal email, for instance an or address.  So when Joe User recieves the newsletter it appears it came from Joe RealEstateAgent.

In some cases our users have Contacts that are invalid email addresses.

Since our application Smart Hosts ALL system messages through our Exchange 2003 server, when an NDR is generated it is Generated by our Exchange server.

Now to the problem that I am facing:

The NDR is generated but is not being delivered to the proper place.  I am able to view the NDR and the 'To:' Field says the correct address however, it is not arriving there ever.

If the address that the NDR is going to exists as a user in our domain however, the message will arrive at the correct recepient.

I understand if no one can help me, I am pretty self-sufficient and I know I can probably eventually figure it out, but I know there are some brilliant minds on this site and figured I would give it a shot.

Any help is appreciated.

Thank You,

Question by:1Parkplace
    LVL 2

    Expert Comment

    Is your app using MAPI or SMTP to attempt its delivery?  If it's MAPI, it will never try to get the NDR out; but if it's SMTP, and relaying is allowed, perhaps it will.

    I would turn up diagnostics logging to a high level, try again, and take a look in the application event log.  Guaranteed you see the error for delivery of your NDR and the exact reason will show there.

    LVL 104

    Expert Comment

    At first glance, what you are seeing appears to be by design.

    You are masking the from field. That basically means that you are spoofing the from field - which is generally considered a very bad thing. However if the From address is inaccurate, because it is the same as the To: field, then what is Exchange going to do with the NDR? Who can it deliver the NDR to? It can't deliver it to the "sender" because the sender doesn't exist - because you have told Exchange the sender is the same person who the message is to!

    What is your reason for wanting to mask the from address?
    What you are doing is a common spammers trick and many sites will block the messages on that basis. I have clients who have seen a significant drop in the spam their users receive by simply blocking messages that appear to come from their own domain.


    Author Comment


    We only mask the address of the sender because the Real Estate agents want the newsletters to look like it is coming from them.

    Let's say for instance we have an Agent that has  We put that in to their profile.

    Now let's say that they have a contact in their database that is

    Now, Let's say that doesn't exist...  What we are trying to do is have the NDR get back to, However this is not happening.

    The test I have done is set the Email Address to an internal email address that belongs to a user account on our network.  The NDR successfully arrives to myself when attempting to send to

    As Soon as the email address in the users profile is changed to something that does not exist in our active directory, The NDR will never arrive.
    LVL 104

    Accepted Solution

    I am pretty sure that you aren't going to get it to work in the way that you want.

    That is a form of relaying - which is why the messages aren't going out. Exchange doesn't recognise the recipient - because they are in the separate database, so drops the message.

    I don't even think that a mail enabled contact with an email address on your domain and the external email address would work either - although you could try that.
    Make sure that you configure it correctly... otherwise you will cause an email loop.


    Author Comment

    The interesting thing about this issue, is that if I set the Default SMTP Service on the Exchange server to Copy ALL NDR's to a specific address which in this case is  I can see the NDR that is generated and in the TO: Field it says the correct outbound address .... So why is it not going there ...
    LVL 104

    Expert Comment

    The NDR will always be generated - it is being dropped later in the process.

    If it is that key to your business then you will need to speak to Microsoft - perhaps through the developer support channels.


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