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The System Attendant homeMDB attribute is missing

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at https://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2010-04-01

The Microsoft Exchange Best Practices Analyzer examines the Active Directory directory service to determine whether the Microsoft Exchange System Attendant service has the homeMDB attribute set. If the Exchange Best Practices Analyzer cannot locate the homeMDB attribute value, the tool generates the following message:

The 'homeMDB' value for the Microsoft Exchange System Attendant service on server <ExchangeServerName> is missing. This will cause reliability problems.

Note

If there is no mailbox store on the server, the Exchange Best Practices Analyzer does not generate the error message.

If the System Attendant homeMDB value is missing, you may experience the following symptoms in your Exchange environment:

  • The System Attendant mailbox appears under Disconnected Mailboxes in the Exchange Management Console.

  • Users are unable to retrieve the free/busy information for Exchange users. If you enable logging in Microsoft Office Outlook 2007, the following information is logged in the %TEMP%\olkas\Free/Busy log file:

    xmlns="https://schemas.microsoft.com/exchange/services/2006/errors">5008</ExceptionCode></MessageXml></ResponseMessage><FreeBusyView>

    Note

    Error code 5008 corresponds to a "MailboxLogonFailed" error.

  • Search Indexing fails with a "MapiExceptionUnknownUser" error. In this scenario, the following event is logged in the Application log:

    Event Type: Warning

    Event Source: MSExchange Search Indexer

    Event Category: General

    Event ID: 107

    Date: <date>

    Time: <time>

    User: N/A

    Description:

    Exchange Search Indexer has temporarily disabled indexing of the Mailbox Database

    First Storage Group\Mailbox Database (GUID = <GUID>)

    due to an error [Microsoft.Mapi.MapiExceptionUnknownUser]: MapiExceptionUnknownUser:

    Unable to make connection to the server. (hr=0x80004005, ec=1003)

  • When you perform MAPI connectivity tests by running a cmdlet, such as the test-mapiconnectivity -verbose cmdlet, you receive a "Microsoft.Mapi.MapiExceptionUnknownUser" result.

The System Attendant mailbox is required for Outlook clients to obtain free/busy information from Exchange. Additionally, the System Attendant mailbox is required for mailbox move operations. If the System Attendant mailbox is not available, event ID 9175 is logged in the Application log. The homeMDB attribute represents the distinguished name (also know as DN) of the Exchange database that hosts the System Attendant mailbox. If this value is missing, the System Attendant mailbox is unavailable.

To address this issue, use the ADSI Edit tool to determine the distinguished name of the appropriate mailbox database, and then set the System Attendant homeMDB attribute.

To determine the distinguished name of the Exchange database

  1. Start the ADSI Edit tool. To do this, click Start, click Run, type adsiedit.msc, and then click OK.

    Note

    In Windows Server 2008, ADSI Edit is installed by default. In Windows Server 2003, ADSI Edit is included with the Windows Support Tools. To install the Windows Support Tools, double-click Suptools.msi in the Support\Tools folder on the Windows Server 2003 CD.

  2. Connect to the Configuration container if ADSI Edit is not already connected. To do this, follow these steps:

    1. On the Action menu, click Connect to.

    2. In the Select a well known Naming Context list, click Configuration, and then click OK.

  3. Expand the following path:

    • Configuration [<domainController>.contoso.com]

    • CN=Configuration,DC=contoso,DC=com

    • CN=Services

    • CN=Microsoft Exchange

    • CN=<OrganizationName>

    • CN=Administrative Groups

    • CN=Exchange Administrative Group (<ID>)

    • CN=Servers

    • CN=<MailboxServerName>

    • CN=Information Store

    • CN=<StorageGroupName>

  4. In the details pane, right-click the CN=<DataBaseName> entry that has a Class value of msExchPrivateMDB, and then click Properties.

  5. On the Attribute Editor tab, click distinguishedName, and then click View.

  6. Copy the path that appears in the Value box, and then click Cancel.

  7. Click Cancel, and then exit the ADSI Edit tool.

To set the homeMDB attribute

  1. Start the ADSI Edit tool. To do this, click Start, click Run, type adsiedit.msc, and then click OK.

    Note

    In Windows Server 2008, ADSI Edit is installed by default. In Windows Server 2003, ADSI Edit is included with the Windows Support Tools. To install the Windows Support Tools, double-click Suptools.msi in the Support\Tools folder on the Windows Server 2003 CD.

  2. Connect to the Configuration container if ADSI Edit is not already connected. To do this, follow these steps:

    1. On the Action menu, click Connect to.

    2. In the Select a well known Naming Context list, click Configuration, and then click OK.

  3. Expand the following path:

    • Configuration [<domainController>.contoso.com]

    • CN=Configuration,DC=contoso,DC=com

    • CN=Services

    • CN=Microsoft Exchange

    • CN=<OrganizationName>

    • CN=Administrative Groups

    • CN=Exchange Administrative Group (<ID>)

    • CN=Servers

    • CN=<MailboxServerName>

  4. In the details pane, right-click CN=Microsoft System Attendant, and then click Properties.

  5. On the Attribute Editor tab, click homeMDB, and then click Edit.

  6. Type or paste the distinguishedName value into the Value box, and then click OK. This value resembles the following:

    CN=Mailbox Database,CN=<StorageGroupName>,CN=InformationStore,CN=<MailboxServerName>,CN=Servers,CN=Exchange Administrative Group (<ID>),CN=Administrative Groups,CN=<OrganizationName>,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=contoso,DC=com

  7. Exit the ADSI Edit tool.

  8. On the affected Exchange server, restart the Microsoft Exchange System Attendant service.