Outlook may receive a full download of the offline address book when the Recipient Update Services in Exchange Server 2003 is under a heavy load

Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:If a situation occurs where a mail-enabled object has a blank legacyExchangeDN attribute when the Offline Address book generates, you may receive the following event logs in the Application log:

Event ID: 9340

Event Type: Warning
Event Source: MSExchangeSA
Event Category: OAL Generator
Event ID: 9340
Description: A new parent Legacy Exchange DN container value '/o=NT5/ou=BBA398C1936B714BA8665C17BAEF3E1F' was found during generation of the differential update file for offline address list \Global Address List . This will force clients using this offline address list to do a full download of the offline address list - Default Offline Address List

Event ID: 9116

Event Type:Warning
Event Source: MSExchangeSA
Event Category: OAL Generator
Event ID: 9116
Description: OALGen encountered an error while generating the changes.oab file for differential downloads of address list '\Global Address List'. Clients will not be able to incrementally update to the new version of the offline address list. This is typical if this is the first time this offline address list has been generated. Check other logged events to see whether this is a serious error - Default Offline Address List

In this situation, Microsoft Outlook may receive a full download of the offline address book instead of an incremental download. This problem can occur in either Mixed mode or Native mode. For more information, see the "More Information" section.

Service pack information

To resolve this problem, obtain the latest service pack for Microsoft Exchange Server 2003. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.Because of file dependencies, this hotfix requires Microsoft Exchange Server 2003 Service Pack 1 (SP1).

Note To enable this hotfix, you must set the OAL NT5 DN Rejection registry value. To do this, follow these steps.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

1. Click Start, click Run, type regedit in the Open box, and then click OK.
2. Locate and then click to select the following registry key:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeSA\Parameters
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type OAL NT5 DN Rejection, and then press ENTER.
5. Right-click OAL NT5 DN Rejection, and then click Modify.
6. In the Value data box, type 0x1 (1).
7. Quit Registry Editor.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This problem was first corrected in Exchange Server 2003 Service Pack 2.

Typically, the legacyExchangeDN attribute is populated when an object is created. If the legacyExchangeDN attribute is cleared, the Recipient Update Service (RUS) should almost immediately re-populate it. It is be very unlikely that this behavior could occur. However, this behavior occurs if the following conditions are true:

• If you use ADSIEdit or performan LDAP import into Active Directory directory services, the legacyExchangeDN attribute of an object is cleared. The RUS server is under very heavy load at the time that the legacyExchangeDN attribute is cleared. Additionally, the Offline Address List is generated.
• If the legacyExchangeDN attribute is cleared while the RUS is disabled or is not scheduled to run, the Offline Address List generates before the RUS is reenabled.

Because Offline Address List generation finds an object with a blank legacyExchangeDN attribute, it assumes a that the legacyExchangeDN attribute based on the ObjectGUID attribute of the domain that object resides in. Therefore, the object does not actually have this assumed DN set, it is only assumed by the Offline Address List generation. Because this new DN represents a change to the Parent DN table, generation of the incremental Offline Address List fails. This behavior causes a full download for Outlook users.

Later, the RUS may correctly stamp the legacyExchangeDN attribute for the user. This would cause the assumed DN to be removed from the parent DN table. Therefore, you may find that the following events at the next Offline Address List generation:

This means that the incremental Offline Address List has again failed to generate. This behavior causes another full download for Outlook users.