You receive the "HTTP 1.1/ 503 Service is no longer available" error message when users try to access Exchange 2000 or Exchange Server 2003 public folders by using Outlook Web Access

After you install and configure a Microsoft Exchange 2000 front-end server or a Microsoft Exchange Server 2003 front-end server, Exchange 2000 users and Exchange Server 2003 users who connect to the front-end server cannot access the Exchange public folders by using Microsoft Outlook Web Access (OWA). Users who try to do this may receive the following error message: When you try to use Exchange System Manager to access the public folders on the Exchange 2000 front-end server or on the Exchange Server 2003 front-end server, the public folders cannot be accessed. You may receive the following error message:

This problem typically occurs when the public folder on the Exchange 2000 front-end server or on the Exchange Server 2003 front-end server has been associated with the following:

• A non-existent public folder on another Exchange 2000 Server computer or on another Exchange Server 2003 computer
• An Exchange 2000 Server computer or an Exchange Server 2003 computer that is not reachable
• An Exchange 2000 Server computer or an Exchange Server 2003 computer that does not host public folders

This problem may also occur when the local path for the Public virtual folder does not match the physical path of the Exchange Installable File System (ExIFS) drive in Windows Explorer.

Note With ExIFS, you can view and use the Exchange Server information store as a file system. In Exchange 2000, the M drive is a convenient handle for ExIFS. However, ExIFS can use a drive other than the M drive.

To resolve this issue, use the ADSI Edit tool to view the contents of the msExchOwningPFTreeBL object in Active Directory on the Exchange 2000 back-end server or on the Exchange Server 2003 back-end server, and then use ADSI Edit to verify that the msExchOwningPFTreeBL property value is correct. Also, verify that the msExchOwningPFTreeBL property value is the same for each administrative group.

Note ADSI Edit is available in the Support folder on the Windows 2000 CD-ROM.

To verify the msExchOwningPFTreeBL property value, follow these steps:

1. Click Start, click Run, type mmc in the Open box, and then click OK.
2. In the MMC console, click Console, and then click Add/Remove Snap-in.
3. In the Add/Remove Snap-in dialog box, click Add.
4. In the Add Stand-alone Snap-in dialog box, click ADSI Edit, click Add, and then click Close.
5. In the Add/Remove Snap-in dialog box, click Close.
6. In the ADSI Edit console, right-click ADSI Edit, and then click Connect to.
7. In the Connection Settings dialog box, click Select a well-known naming context, click Configuration container in the list, and then click OK.
8. In the ADSI Edit console, expand CN=Configuration Container, expand CN=Configuration, expand CN=Services, expand CN=Microsoft Exchange, expand CN=Administrative Group, and then expand CN=Folder Hierarchies.
9. In the right pane, right-click CN=Public Folders, and then click Properties.
10. In the CN=Public Folders dialog box, click the Select a Property to view list, and then click the msExchOwningPFTreeBL property. Make sure that the msExchOwningPFTreeBL property value points to an existing Exchange 2000 server or Exchange Server 2003 server that holds the public folders.
11. In the CN=Public Folders dialog box, click Remove to change the msExchOwningPFTreeBL property value. When you have finished modifying the msExchOwningPFTreeBL property value, click Add.
12. Repeat these steps for each administrative group.
13. Restart the Exchange 2000 front-end server.

If the msExchOwningPFTreeBL property value is valid, there may be an incorrect physical path for the public folders in Microsoft Internet Information Services (IIS) on the Exchange front-end server. To verify the physical path for the public folders in IIS, follow these steps:

1. Click Start, point to Programs, click Administrative Tools, and then click Internet Services Manager.
2. In Internet Information Services, expand Default Web Site, and then right-click the virtual folder that is named Public.
3. In the Public properties dialog box, verify that the Local Path setting points to the correct physical path for the public folders on the Exchange 2000 back-end server or on the Exchange Server 2003 back-end server. For example, the path might be the following: m:\contoso.com\Public Folders.
4. If the Local Path setting does not point to the correct physical path, click Browse, and then locate the correct physical path for the Exchange public folders.

This behavior is by design.

For additional information about troubleshooting '503 Service Unavailable' errors, click the following article number to view the article in the Microsoft Knowledge Base: For additional information about "HTTP/1.1 503 Service Unavailable" errors, click the following article number to view the article in the Microsoft Knowledge Base: