How to troubleshoot the "503 service unavailable" error message in Outlook Web Access 2000 (305030)


The information in this article applies to:

  • Microsoft Exchange 2000 Server
This article was previously published under Q305030
Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry

SUMMARY

After you type the address to Microsoft Outlook Web Access (OWA) on a Microsoft Exchange 2000 Server computer, you may receive the following error message on your browser before you receive the OWA log on prompt:
503 Service Unavailable
This error message indicates that the Davex.dll file cannot communicate with either a mailbox store or a public folder store.

MORE INFORMATION

The "503 Service Unavailable" error message can occur if the following conditions are true:
  • The Exchange 2000 Server services are not running, particularly the system attendant and the information store. Make sure that all of the services are running.
  • The Exchange 2000 Server services are running but not under the local system account. The services must be running under the local system account.
  • The mailbox stores and public folder stores that you are trying to gain access to are not mounted. Therefore, you must mount the mailbox stores and the public folder stores.
  • A registry key exists in the HKEY_CLASSES_ROOT registry hive that exceeds 259 characters. Throughout initialization, the Exchange OLE DB provider (ExOLEDB) scans the HKEY_CLASSES_ROOT hive to identify registered file types. If any subkey has a default value that exceeds 259 characters, or if there is a discretionary access control list (DACL) that is not valid on one of the subkeys, ExOLEDB may quit unexpectedly.

    If this is the issue, the following series of event ID messages are logged in the Application event log when you restart the Exchange 2000 Server services:

    Event Type: Information
    Event Source: MSExchangeSA
    Event Category: General
    Event ID: 9014
    Description:
    Microsoft Exchange System Attendant has been started for Exchange server servername successfully.

    Event Type: Information
    Event Source: MSExchangeSA
    Event Category: Monitoring
    Event ID: 9095
    Description:
    The MAD Monitoring thread is initializing.

    Event Type: Information
    Event Source: MSExchangeSA
    Event Category: Monitoring
    Event ID: 9096
    Description:
    The MAD Monitoring thread is initialized.

    Event Type: Information
    Event Source: EXOLEDB
    Event ID: 101
    Description:
    Microsoft Exchange OLEDB has successfully shutdown.

    Event Type: Error
    Event Source: MSExchangeIS
    Event ID: 9542
    Description:
    Initialization of external interface OLEDB failed; Error ecServerOOM.

    Additionally, the following event ID message may be logged in the Application event log multiple times. The Microsoft Exchange Free-and-Busy Publishing service may also generate some errors:

    Event Type: Error
    Event Source: EXCDO
    Event Category: General
    Event ID: 8206
    Description:
    Calendaring agent failed with error code 0x800XXXXX while saving appointment.

    The following event ID message may be logged in the System Log multiple times:

    Event Type: Error
    Event Source: DCOM
    Event Category: None
    Event ID: 10002
    Description:
    Access denied attempting to launch a DCOM Server. The server is: {9DA0E106-86CE-11D1-8699-00C04FB98036} The user is SYSTEM/NT AUTHORITY, SID=S-1-5-18

    The event ID 1005 message is the most important. It indicates that initialization of external interface OLEDB (Exoledb.dll) is not responding.
  • A Group Policy object (GPO) exists that is restricting the MSExchangeIS service from initializing. You may notice the event ID messages Event 101 EXOLEDB and Event 9542 MSExchangeIS, such as in the fourth bulleted item.

    Note The descriptions of the event ID messages may be different.

    You may also notice the following event ID messages:

    Event Type: Error
    Event Source: EXCDO
    Event ID: 8208
    Description:
    Calendaring agent failed with error code 0x8000ffff while expanding recurring appointments.

    -and-

    Event Type: Error
    Event Source: DCOM
    Event ID: 10009
    Description:
    DCOM was unable to communicate with the computer RCC-EXH-02-W using any of the configured protocols.

    If this is the scenario, because it is not easy to remove a GPO, which can cause security concerns, to work around this issue follow these steps:

    Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
    1. Export the following registry key for back up:

      [HKEY_CLASSES_ROOT\AppID\{9DA0E0EA-86CE-11D1-8699-00C04FB98036}] "LocalService"="MSEXCHANGEIS"
    2. Delete the following registry key:

      [HKEY_CLASSES_ROOT\AppID\{9DA0E0EA-86CE-11D1-8699-00C04FB98036}] "LocalService"="MSEXCHANGEIS"
    3. In the DCOM Configuration utility (Dcomcnfg.exe), set the Identity tab on the ExOLEDB DCOM Service to The launching user. To do so:

      Note You must complete the previous step before you proceed to this step.
      1. Click Start, click Run, type dcomcnfg, and then click Open.
      2. Click ExOLEDB Session Factory.
      3. Click the Properties button, and then click the Identity tab.
      If this work-around resolves the "503 Service Unavailable" error for OWA, the issue is related to a GPO, and you can consider changing or removing the problematic GPO. If these steps do not resolve the "503 Service Unavailable" error, import the registry key that you exported and deleted. Permanent removal of this registry key can cause other issues on the server if the issue is not related to a GPO.
    4. If you are viewing 101 EXOLEDB event ID messages and 9542 MSExchangeIS event ID messages such as following, some MDAC components may be incorrectly registered, and you must re-register them:

      Event Type: Information
      Event Source: EXOLEDB
      Event ID: 101
      Description:
      Microsoft Exchange OLEDB has successfully shutdown.

      -and-

      Event Type: Error
      Event Source: MSExchangeIS
      Event ID: 9542
      Description:
      Initialization of external interface OLEDB failed; Error Unknown error.
    The following is a list of the .dll files that you must have so that you can re-register to resolve this issue. You must stop the Information Store service before you re-register, and then you can restart the Information Store service after you successfully register the following .dll files:
    • C:\Program Files\Common Files\System\Ole DB\oledb32.dll
    • C:\Program Files\Common Files\System\Ole DB\Oledb32r.dll
    • C:\Program Files\Common Files\System\Ole DB\Msdaipp.dll
    • C:\Program Files\Common Files\System\ado\Msado15.dll
    • C:\Program Files\Common Files\System\Ole DB\Msdaurl.dll
    To register a .dll file, at a command prompt, type regsvr32 followed by the path to and name of the .dll file. For example, to re-register the Oledb32.dll file in the first bulleted item, type the following command:

    regsvr32 c:\program~1\common~1\system\oledb~1\oledb32.dll
Modification Type:MinorLast Reviewed:7/21/2005
Keywords:kbinfo KB305030
©2004 Microsoft Corporation. All rights reserved.