XWEB: Troubleshooting HTTP 401.x Errors in Outlook Web Access 5.5 (317627)


The information in this article applies to:

  • Microsoft Outlook Web Access 5.5 SP 3
  • Microsoft Outlook Web Access 5.5
  • Microsoft Outlook Web Access 5.5 SP 1
  • Microsoft Outlook Web Access 5.5 SP 2
This article was previously published under Q317627

SUMMARY

This article describes some of the various reasons that you may receive a "401 Unauthorized" error message when you are using Microsoft Outlook Web Access (OWA). This article also provides some common methods that you can use to try to resolve such an error.

MORE INFORMATION

Microsoft Windows NT Server 4.0

401.1 - Unauthorized: Logon Failed

This error may occur for the following reasons:
  • Local security policies. Every OWA user requires access to two local security policies:
    • The first local security policy is "Log On Locally." To make sure that your users have this setting enabled:
      1. Start User Manager for Domains.
      2. On the Policies menu, click User Rights.
      3. In the User Rights dialog box, click Log on Locally.
      4. In the Grant To box, add a domain group that your users belong to. Typically, this group is the Domain Users group. Adding such a domain group ensures that your users have access to log on locally.

        NOTE: If Exchange is running on a member server, the change must be made to the local security policy for that server. To bring up the server's local security policy, click Start, click Run, and then type usrmgr localservername.
    • The second local security policy is "Access This Computer From the Network." To make sure that your users have this setting enabled:
      1. Start User Manager for Domains.
      2. On the Policies menu, click User Rights.
      3. In the User Rights dialog box, click Access This Computer From the Network.
      4. In the Grant To box, add a domain group that your users belong to. Typically, this group is the Domain Users group. Adding such a domain group allows your OWA users access through this policy.
  • Basic authentication and the Windows NT domain name. OWA supports two authentication methods. Those methods are "Basic" and "Windows NT Challenge Response (NTLM)". If you use the Basic authentication method in OWA and you do not supply a default domain name, you may receive this error message because the domain is omitted in the credentials dialog box.

    To determine whether or not you are experiencing this issue, after you type your mailbox name in OWA, look at the credentials dialog box. If two boxes are displayed (User name and Password), you are probably using Basic authentication. If three boxes are displayed (User name, Password, and Domain), you are probably using NTLM authentication.

    The exception to this rule is Microsoft Internet Explorer 6. If you use Internet Explorer 6, only the User name and Password boxes are displayed in the credentials dialog box, even if you are using NTLM authentication.

    After you determine that you are using Basic authentication, try using the following format for your logon information:
    • User name:

      Windows_NT_domain_name\user_name (for example, microsoft\user1)

    • Password:

      user's_password

    If you can use the preceding format to log on without receiving the 401.1 error message, to avoid this issue in the future, either:

    • Instruct your users to log on by using that format. -or-

    • Add a default domain in the Basic authentication section of Internet Information Services (IIS) for OWA:
      1. On the OWA server, start Internet Services Manager.
      2. Expand the Web site in which OWA is installed, right-click the Exchange virtual directory, and then click Properties.
      3. Click the Directory Security tab, and then click Edit next to Anonymous access and Authentication Control.
      4. Click Edit next to Basic authentication.
      5. Use one of the following steps, as appropriate:
        • If all of your user accounts exist in one Windows NT domain, type that domain name in the Default Domain box. -or-

        • If your user accounts are spread among multiple domains, it is easier to type \ in the Default Domain box. If you type \ in the Default Domain box, OWA searches all of the trusted domains for the user name.
      After you add a default domain, the users can gain access to OWA by just supplying their user name and password, instead of typing domain\user_name.

  • File-level antivirus scanning software. A file-level antivirus scanning utility that is actively scanning the Exchsrvr folder on the hard disk can also cause this error. This issue can also manifest itself as a blank screen in the Web browser, instead of as an error message.

    At a minimum, exclude the Exchsrvr\Mdbdata, Exchsrvr\Webdata, and Exchsrvr\Webtemp folders from file-level antivirus scans. If you do not exclude these folders, issues may occur with both OWA and MAPI clients. Refer to your antivirus software's documentation for instructions about how to exclude files and folders.

    If you are concerned about mail-related viruses in Microsoft Exchange Server, obtain antivirus software which is "Exchange Server-aware". Exchange Server-aware antivirus software uses scanning methods for the Exchange Server store that are not damaging. Exchange Server-aware antivirus software uses the antivirus application programming interface (API) that is built into Exchange Server.

401.3 - Unauthorized Due to ACL on Resource

This error is usually the result of not having the required NTFS security permissions on a file or registry key. To determine if this error is the result of not having the required NTFS security permissions:
  1. Confirm that the Everyone group has at least the minimum permissions that are required on the folders in the following table. To view the permissions on a folder, open the properties of the folder, and then click the Security tab. If the Security tab is missing, the folder resides on a file allocation table (FAT) partition. There are no specific file-level permissions on a FAT partition. If the folder is on a FAT partition, skip to step 2 (registry permissions).

    FolderPermission
    X:\ExchsrvrRead
    X:\Exchsrvr\WebdataChange
    X:\Exchsrvr\WebtempChange
    X:\Exchsrvr\BinRead
    X:\Exchsrvr\ResRead
    X:\WinntRead
    X:\Winnt\System32Read
  2. Confirm that the Everyone group has at least the minimum permissions required on the registry keys in the following table. To view security settings on registry keys:

    1. Click Start, and then click Run.
    2. In the Run dialog box, type regedt32.exe.
    3. Click the registry key that you want to view the security settings for, and then click Permissions on the Security menu.
    Registry keyPermission
    HKEY_LOCAL_MACHINE\system\currentcontrolset\services\MSExchangeWebRead
    HKEY_LOCAL_MACHINE\system\currentcontrolset\services\W3svcRead

Microsoft Windows 2000 Server

401.1 - Unauthorized: Logon Failed

This error may occur for the following reasons:
  • Local security policies. Every OWA user requires access to two local security policies:
    • The first security policy is "Log On Locally." To make sure that your users have this setting turned on:
      1. Start the Local Security Policy snap-in.

        NOTE: If OWA is installed on a Windows 2000-based computer that is a domain controller, start the Domain Controller Security Policy snap-in.
      2. Expand Local Policies, and then expand User Rights Assignment.
      3. In the right pane, click Log on Locally.
      4. In the Assign To box, add a domain group that your users belong to. Typically, this group is the Domain Users group. Adding such a domain group ensures that your users have access to log on locally.
    • The second Local Security Policy is "Access This Computer From the Network." To make sure that your users have this setting turned on:
      1. Start the Local Security Policy snap-in.

        NOTE: If OWA is installed on a Windows 2000-based computer that is a domain controller, start the Domain Controller Security Policy snap-in.
      2. Expand Local Policies, and then expand User Rights Assignment.
      3. In the right pane, click Access This Computer From the Network.
      4. In the Assign To box, add a domain group that your users belong to. Typically, this group is the Domain Users group. Adding such a domain group allows your OWA users access through this policy.
  • Basic authentication and the Windows NT domain name. OWA supports two authentication methods. Those methods are "Basic" and "Windows NT Challenge Response (NTLM)." If you use the Basic authentication method in OWA and you do not supply a default domain name, you may receive this error message because the domain name is omitted in the credentials dialog box.

    To determine whether or not you are experiencing this issue, after you type your mailbox name in OWA, view the credentials dialog box. If two boxes are displayed (User name and Password), you are probably using Basic authentication. If three boxes are displayed (User name, Password, and Domain), you are probably using NTLM authentication.

    The exception to this rule is Internet Explorer 6. If you use Internet Explorer 6, only the User name and Password boxes are displayed in the credentials dialog box, even if you are using NTLM authentication.

    After you determine that you are using Basic authentication, try using the following format for your logon information:

    • User name:

      Windows_NT_domain_name\user_name (for example, microsoft\user1)

    • Password:

      user's_password

    If you can use the preceding format to log on without receiving the 401.1 error message, to avoid this issue in the future, either:
    • Instruct your users to log on by using that format. -or-

    • Add a default domain in the basic authentication section of IIS for OWA:
      1. On the OWA server, start Internet Services Manager.
      2. Expand the Web site in which OWA is installed, right-click the Exchange virtual directory, and then click Properties.
      3. Click the Directory Security tab, and then click Edit next to Anonymous access and Authentication Control.
      4. Click Edit next to Basic authentication.
      5. Use one of the following steps, as appropriate:
        • If all your user accounts exist in one Windows NT domain, type that domain name in the Default Domain box. -or-

        • If your user accounts are spread among multiple domains, it is easier to type \ in the Default Domain box. If you type \, OWA searches all of the trusted domains for the user name.
      After you add a default domain, the users can gain access to OWA by just supplying their user name and password, instead of typing domain\user_name.

  • File-level antivirus scanning software. A file-level antivirus scanning utility that is actively scanning the Exchsrvr folder on the hard disk can also cause this error. This issue can also manifest itself as a blank screen in the Web browser, instead of as an error message.

    At a minimum, exclude the Exchsrvr\Mdbdata, Exchsrvr\Webdata, and Exchsrvr\Webtemp folders from file-level antivirus scans. If you do not exclude these folders, issues may occur with both OWA and MAPI clients. Refer to your antivirus software's documentation for instructions about how to exclude files and folders.

    If you are concerned about mail-related viruses in Exchange Server, obtain antivirus software that is "Exchange Server-aware." Exchange Server-aware software uses scanning methods for the Exchange Server store that are not damaging. Exchange Server-aware antivirus software uses the antivirus application programming interface (API) that is built into Exchange Server.
  • OWA is installed on Windows 2000. Users who log on to OWA from a computer that is running any Microsoft Windows operating system other than Windows 2000 can gain access to OWA, but users who log on to OWA from a computer that is running Windows 2000 may receive a 401.1 error message.

    This issue can occur if OWA is installed on a computer that is running Windows 2000 Server with Integrated Windows Authentication turned on as one of the authentication methods on the Exchange Server virtual directory.

    To resolve this issue, on the server that OWA is installed on, edit the Constant.inc file in the Exchsrvr\Webdata\Usa folder:

    1. Use Notepad to open the Constant.inc file.
    2. Under '--Other Strings--', locate the following line:

      bstrAuthTypesAccepted = "_BasicNTLMDPAMBS_BASIC"

    3. Change the line to read:

      bstrAuthTypesAccepted = "_BasicNTLMDPAMBS_BASICNegotiate"

    4. On the File menu, click Save.
    5. On the File menu, click Exit.
    If you use a computer that is running either Microsoft Windows 2000 Server and Internet Explorer 5 or Microsoft Windows 2000 Professional and Internet Explorer 5 to try to log on to Internet Information Service (IIS) 5.0, and Integrated Windows Authentication is enabled, a negotiation is performed to determine if the Kerberos protocol or Windows NT Challenge/Response will be used for authentication.

    If you use a computer that is running either Windows 2000 Server and Internet Explorer 5 or Windows 2000 Professional and Internet Explorer 5, the server variable AUTH_TYPE is set to Negotiate. When you use a computer that is running any other Windows operating system, the server variable is set to NTLM. OWA checks what this variable returns against the bstrAuthTypesAccepted value that is modified. This check ensures that the authentication type is acceptable before OWA allows a user to log on.

401.3 - Unauthorized Due to ACL on Resource

This error is usually the result of not having the required NTFS security permissions on a file or registry key. To determine if this error is the result of not having the required NTFS security permissions:
  1. Confirm that the Everyone group has at least the minimum permissions that are required on the folders in the following table. To view the permissions on a folder, open the properties of the folder, and then click the Security tab. If the Security tab is missing, the folder resides on a FAT partition. There are no specific file-level permissions on a FAT partition. If the folder is on a FAT partition, skip to step 2 (registry permissions).

    FolderPermission
    X:\ExchsrvrRead
    X:\Exchsrvr\WebdataChange
    X:\Exchsrvr\WebtempChange
    X:\Exchsrvr\BinRead
    X:\Exchsrvr\ResRead
    X:\WinntRead
    X:\Winnt\System32Read
  2. Confirm that the Everyone group has at least the minimum permissions that are required on the registry keys in the following table. To view security settings on registry keys:

    1. Click Start, and then click Run.
    2. In the Run dialog box, type regedt32.exe.
    3. Click the registry key that you want to view the permissions for, and then click Permissions on the Security menu.
    Registry keyPermission
    HKEY_LOCAL_MACHINE\system\currentcontrolset\services\MSExchangeWebRead
    HKEY_LOCAL_MACHINE\system\currentcontrolset\services\W3svcRead
Modification Type:MinorLast Reviewed:11/21/2005
Keywords:kbhowto KB317627
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