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MS Exchange 2003 NDR generated when mailing to users with non-local adresses

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  • MS Exchange 2003 NDR generated when mailing to users with non-local adresses

    Hi all;

    First the situation:

    The company I currently work for has different sites throughout the country. One site 'owns' the MX record and has a POP3 server that serves mail for the entire organisation. Other sites connect to that server to get their mails. I'm @ one of those other sites.

    Because management team insisted on extra functionality we rolled out exchange and we're in progress of migrating the users. We simply set up forwarding on the POP3 server (forwarding to external IP of our exchange through a leased line) on per-user basis. Some of the users are on exchange and some still use POP3. We use the same e-mail domain.


    Microsoft Exchange 2003 Standard SP2, running on Windows 2003 standard VMWare machine. Both fully patched. At this time no antivirus or antispam software running (the POP3 site is taking care of that).


    I need to add two users to a distribution group. Those two users do not have an exchange mailbox at this time. I estabilished the mail adresses in Exchange/AD and they're correct when I check 'em in my GAL.
    Exchange server is not authoritive for the mail domain, so in the default recipient policy the checkbox 'this exchange organisation is responsible for all mail delivery to this adress' is not checked. The default policy contains:

    %g.%[email protected] (the same domain as the POP3 site, and the internet MX record)
    %g.%[email protected] (local FQDN)

    all checked.

    In the configuration of the Default SMTP Virtual Server Properties I have specified the SMTP server on the main site on the Messages - Forward All Mail With Unresolved Recipients To Host tabpage.

    As long as I do not estabilish an e-mail adress on a user, or do not add the user to a local distribution list everyhthing works fine. If I mail from an exchange account to a user on the same mail domain, exchange checks the local store first, and the it forwards the message to the smtp server on the main site and that server delivers the mail to the POP3 mailbox - so far, so good.

    However, if I estabilish an e-mail address, OR create a contact for a user with the same e-mail domain (different physical site) OR add a contact or a user to a distribution group then sending mail to that user becomes impossible.

    I get the following NDR:

    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.
    <VMSRVEXCH01.gsc01.local #5.4.6>

    I also get the following event in the event logs:

    A non-delivery report with a status code of 5.4.6 was generated for recipient x-ex;/O=DSV SOLUTIONS/OU=FIRST ADMINISTRATIVE GROUP/CN=RECIPIENTS/CN=PCLAES (Message-ID <[email protected] 1.gsc01.local>).
    Cause: A forward loop was detected by the categorizer. This is a common hosting configuration problem caused when someone uses the provisioning tool to create a contact in one organization unit and creates a user in a different organization user that share the same e-mail address.
    Solution: Verify that you do not have a user in organizational unit and a contact in a different organizational unit that have the same e-mail address.

    I hope this all is making at least some sense...
    Jsut to be clear: our site has doesn't own a MX record. MX record points to another site where a POP3 server contains all the mailboxes for the company. We use forwarding to get the mail to our exchange. Our exchange is not authorative for the mail domain, and forwards everything that hasn't been locally resolved to the SMTP server using a fqdn. Everthing works fine, as long as users without exchange mailboxes do not enter GAL or are not added to a distribution group.

    I actually just started with sys administration on this level (very first project as sysadmin) so be gentle. Any kind of help or suggestion is welcome.
    I think I'm missing something important here, because I used to create contacts for external users with the same e-mail domain on SBS2003, and that worked OK.

    Thnx in advance,


  • #2
    Re: MS Exchange 2003 NDR generated when mailing to users with non-local adresses

    Nevermind, I found the root cause myself:

    When estabilishing a smtp address on exchange the user account's exchange attributes are populated on Exchange General page of the user account. Right after that the Recipient Update Services populates the adresses on the "E-mail adresses" tab of the user account following the default recipient update policy . This causes the user to have two identical addresses and Exchange will be generating a NDR.

    The solution to this particular problem is to remove all the addresses on the "E-mail adresses" tab that were automatically generated and to leave only the smtp address on the Exchange General tab. Also the option to 'Automatically update e-mail adresses based on recipient policy' needs to be unchecked.

    Hope this helps someone... =)