How to troubleshoot the "503 Service Unavailable" error message in Outlook Web Access in Exchange Server 2003

Summary

After you type the address to Microsoft Outlook Web Access (OWA) on a Microsoft Exchange Server 2003 computer, you may receive the following error message in your browser before you receive the OWA log on prompt:
503 Service Unavailable


This problem occurs if the Davex.dll file cannot communicate with a mailbox store or with a public folder store. back to the top

Make sure that all the services are running

The "503 Service Unavailable" error message may occur if the Exchange 2003 services are not running, particularly if the System Attendant service and the Information Store service are not running. To view the services and make sure that all the services are running:
  1. Click Start, point to
    Programs, point to Administrative Tools, and then click Services.
  2. In Services, find Microsoft Exchange Information Store and Microsoft Exchange System Attendant under the Name column, and then look for
    Started under the Status column.
  3. If a service is not started, right-click the service name, and then click Start.
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Make sure that the services are running under the Local System account

The "503 Service Unavailable" error message may occur if the Exchange 2003 services are not running under the Local System account. To make sure that the services are running under the Local System account:
  1. Open Services.
  2. Under the Name column, find
    Microsoft Exchange Information Store and Microsoft Exchange System Attendant, and then look for Local System under the Log On As column.
  3. If a service is not logged on under the Local System account:
    1. Right-click the service name, and then click
      Properties.
    2. Click the Log On tab, and then click
      Local System account under Log On As.
    3. Click OK.
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Mount the mailbox stores and the public folder stores

The "503 Service Unavailable" error message may occur if the mailbox stores and the public folder stores that you want to gain access to are not mounted. Therefore, you must mount the mailbox stores and the public folder stores. To mount the mailbox stores and the public folder stores:
  1. Click Start, point to
    Programs, point to Microsoft Exchange, and then click System Manager.
  2. If the Display administrative groupsoption is turned on, expand Administrative Groups, and then expand First Administrative Group(where First Administrative Group is the name of your administrative group).

    Note To display administrative groups, right-click
    Your_Organization, click
    Properties, click to select the Display administrative groups check box, click OK two times, and then restart Exchange System Manager.
  3. Expand Servers, expand
    Your_Exchange_Server_Name, and then expand First Storage Group.
  4. Right-click Mailbox Store, click
    Mount Store, and then click OK.
  5. Right-click Public Folder Store, click
    Mount Store, and then click OK.
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See if a registry key that exceeds 259 characters exists in the HKEY_CLASSES_ROOT registry hive

The "503 Service Unavailable" error message may occur if a registry key that exceeds 259 characters exists in the
HKEY_CLASSES_ROOT registry hive. During 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 that is not valid on one of the subkeys, ExOLEDB may quit unexpectedly.

If a subkey exceeds 259 characters, or if there is a discretionary access control list that is not valid, the following series of event ID messages are logged in the application event log when you restart the Exchange 2003 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 Free/Busy 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
To help troubleshoot this issue, run the HKCRScan tool (HKCRScan.exe). The HKCRScan tool enumerates the HKEY_CLASSES_ROOT registry hive to locate subkeys that contain more than 259 characters. Additionally, HKCRScan helps determine if there is an invalid discretionary access control list by returning error code 0x5. This error code means "Access denied" when it enumerates a registry key. The HKCRScan tool is an internal tool developed by Microsoft. To obtain this tool, contact Microsoft Product Support Services (PSS). For additional information about how to contact PSS, visit the following Microsoft Web site:
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See if a Group Policy object exists that prevents the MSExchangeIS service from initializing

The "503 Service Unavailable" error message may occur if a Group Policy object (GPO) exists that prevents the MSExchangeIS service from initializing.

You may notice event ID messages that are similar to the Event 101 EXOLEDB and the Event 9542 MSExchangeIS that this article describes.

Note The descriptions of the event ID messages may be different from those that are listed in this article.

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.

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.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
To work around this issue:
  1. Locate and export the following registry key to back it 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. Note You must complete step 2 before you continue to this step.

    In the DCOM Configuration utility (Dcomcnfg.exe), set the
    Identity tab on the ExOLEDB DCOM Service to The launching user:
    1. Click Start, click
      Run, type dcomcnfg, and then click
      OK.
    2. Expand Component Services, and then expand Computers.

      Note The Computers node may take several minutes to expand.
    3. Expand My Computer, and then expand
      DCOM Config.
      You receive the following message:
      The CLSID {9DA0E103-86CE-11D1-8699-00C04FB98036}, item C:\Program Files\Exchsrvr\bin\STORE.EXE and title Exoledb Session Factory has the named value AppID, but is not recorded under \\HKEY_CLASSES_ROOT\AppId. Do you with to record it?
    4. Click Yes.
    5. Under DCOM Config, right-click
      Exoledb Session Factory, and then click
      Properties.

      Important Exoledb Session Factory does not appear if you do not remove the registry key that is described in step 2. Additionally, when you click Properties, the Exoledb Session Factory Properties dialog box may take several minutes to appear.
    6. Click the Identity tab, click
      The launching user, and then click
      OK.
    If this procedure resolves the "503 Service Unavailable" error for OWA, the issue is related to a GPO. You may want to change or remove the GPO that is causing the issue. If this procedure does not resolve the "503 Service Unavailable" error, import the registry key that you exported and then deleted. Permanent removal of this registry key can cause other issues on the server if the issue is not related to a GPO.
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Reregister the MDAC Components

If you view event ID 101 EXOLEDB messages and event ID 9542 MSExchangeIS messages such as the following event ID messages, some Microsoft Data Access Components (MDAC) may be incorrectly registered, and you must reregister them:
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 Unknown error.

The following list contains the .dll files that you must have so that you can reregister the MDAC components to resolve this issue. You must stop the Information Store service before you reregister the files and then restart the Information Store service after you successfully reregister the following .dll files.

Note The Oledb32.dll file version must be 2.8.1022.0 or later.
  • 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:
  • Click Start, click Run, and then type regsvr32 followed by the path and name of the .dll file that you want to register. For example, to reregister the Oledb32.dll file, type the following command at the command prompt:
    regsvr32 "c:\program files\common files\system\ole db\oledb32.dll"
Note When you try to register one of these files, you may receive an error message that is similar to the following:
Load library("path and file name") failed - The specified procedure could not be found
For more information about this scenario, click the following article number to view the article in the Microsoft Knowledge Base:

837285 Users may receive a "503 Service Unavailable" error message in Exchange Server 2003 when they try to use a Web browser to gain access to OWA

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Verify the permissions for the HKEY_CLASSES_ROOT registry key

The default permissions are as follows.
RolePermission
AdministratorsFull Control, Read
Authenticated UsersRead
CREATOR OWNERSpecial Permissions
Server OperatorsRead, Special Permissions
SYSTEMFull Control, Read
Properties

Article ID: 823159 - Last Review: Sep 3, 2013 - Revision: 1

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