Topic Last Modified: 2007-01-23

The Microsoft® Exchange Database Troubleshooter Tool detected an MSExchangeIS 1088 event. This event indicates that the Exchange database could not be mounted because it has a legacyExchangeDN attribute value that is different from what is stored in Active Directory.


An MSExchangeIS 1088 event can occur if an Exchange database is restored to an Administrative Group that has a different value for the legacyExchangeDN attribute than its original Administrative Group. This behavior is by design. To mount stores on an Exchange Server, the value for the legacyExchangeDN attribute of the Organization and the Administrative Group of the Exchange databases must match the value for legacyExchangeDN attribute of the Organization and the Administrative Group in Active Directory.

User Action

To resolve this issue, do the following:

  • Restore the Exchange database to its original Administrative Group.

  • If the Exchange database cannot be restored to its original Administrative Group, rename the Active Directory objects of the intended destination so that they have the same value for the legacyExchangeDN attribute as the Exchange database. You can correct the value using a tool such as Active Directory Service Interfaces (ADSI) Edit, the LDP (ldp.exe) tool, or any other Lightweight Directory Access Protocol (LDAP) version 3 client.

If you incorrectly modify the attributes of Active Directory objects when you use ADSI Edit, the LDP tool, or another LDAP version 3 client, you may cause serious problems. These problems may require that you reinstall Microsoft Windows Server™ 2003, Exchange Server 2003 or Exchange Server 2007, or both. Modify Active Directory object attributes at your own risk.
To correct this error
  1. Using ADSI Edit or a similar tool, locate the administrative group object in Active Directory.

    The legacyExchangeDN attribute can be found at:

    CN=Configuration,CN=Services,CN=Microsoft Exchange,CN=Organization,CN=Administrative Groups,CN=Administrative group

  2. Type a new string value of the form:

    /o= organization /ou= administrative group

For more information about using the LDP tool, see the Microsoft Knowledge Base article 260745, "XADM: Using the LDP Utility to Modify Active Directory Object Attributes" (

For more information about working with ADSI Edit, see the topic "Adsiedit.msc: ADSI Edit" in Windows Server 2003 Help.

For more information about the MSExchangeIS Event 1088, see the following resources: