Categorizer is NDRing a recipient with address : with reason code ().

Product: Exchange
Event ID: 6015
Source: MSExchangeActiveSyncNotify
Version: 6.5.7638.0
Component: Microsoft Exchange Transport
Message: Categorizer is NDRing a recipient with address <%1>:<%2> with reason code <%3> (<%4>).

This error event occurs because all public folder replication that uses Simple Mail Transfer Protocol (SMTP) must originate from an authenticated source or from a server that has been granted Send As permissions.

A common symptom of this error is the generation of a specific non-delivery report (NDR) message. Specifically, you may receive the following NDR message when you try to replicate public folders from a domain that has a Microsoft Exchange Server 5.5 computer or a Microsoft Exchange 2000 Server computer to a domain that has a Microsoft Exchange Server 2003 computer:

    General access denied, sender access denied? The sender of the message does not have the privileges necessary to complete delivery.

MSExchangeTransport Event 9013 may also be logged in the Application log. If it is also logged, there is a specific user action required to resolve the error. To view both these events, set diagnostic logging on the Categorizer category of the MSExchangeTransport service to Maximum.

User Action
  • If you do not see MSExchangeTransport Event 9013 logged with Event 6015, use the information provided in other MSExchangeTransport events to try to resolve this error. If you cannot resolve this error, contact Microsoft Product Support Services.
  • If MSExchangeTransport event 9013 is also logged in the Application log, you can add the SkipPublicMDBRestriction registry key to resolve this error. After you add this registry key, the Exchange Server 2003 computer can process system messages and public folder messages from unauthenticated sources.

      Caution   This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the “Restore the Registry” Help topic in Regedit.exe or Regedt32.exe.

    To resolve this public folder replication issue:

    1. Open a Registry Editor, such as Regedit.exe or Regedt32.exe.
    2. Navigate to HKey_Local_Machine\System\CurrentControlSet\Services\MSExchangeTransport.
    3. Right-click MSExchangeTransport, point to New, and then click Key.
    4. Type Parameters for the name of the new key, and then click Enter.
    5. Right-click Parameters, point to New, and then click DWORD value.
    6. Type SkipPublicMDBRestriction, and then click Enter.
    7. Double-click SkipPublicMDBRestriction.
    8. In Value data, type 1, and then click OK.
    9. Close Registry Editor.

    Before you edit the registry, and for information about how to edit the registry, see Microsoft Knowledge Base article 256986, “Description of the Microsoft Windows Registry” (

  • For additional information about troubleshooting public folder replication problems, see the following Microsoft Knowledge Base articles:


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