In Exchange Server 2003, message delivery to local mailboxes and to external mailboxes is slower than you expect after you configure delivery restrictions based on distribution groups

In Microsoft Exchange Server 2003, message delivery to local mailboxes and to external mailboxes is slower than you expect. Additionally, if you examine the message queues in Exchange System Manager, you see lots of messages that are queued up in the Messages Awaiting Directory Lookup queue.

This problem may occur when the following conditions are true:

1. You send mail to distribution groups.
2. The distribution groups to which you send mail include lots of users who have delivery restrictions configured on their mailboxes. The distribution groups to which you send mail may or may not have nested distribution groups.

Note You configure delivery restrictions on user mailboxes by setting options on the Exchange General tab in Active Directory Users and Computers.

This problem occurs when lots of Lightweight Directory Access Protocol (LDAP) searches are initiated. Lots of LDAP searches are initiated when you send mail to distribution groups that include lots of users who have delivery restrictions configured on their mailboxes.

Note This problem does not occur if you send mail to individual users who have delivery restrictions configured on their mailboxes.

Service pack information

To resolve this problem, obtain the latest service pack for 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.

Prerequisites

You must install Microsoft Exchange Server 2003 Service Pack 1 (SP1) before you install this hotfix.

Restart requirement

You do not have to restart the computer after you install this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

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.

Hotfix installation information

After you install the hotfix that is specified in this article, you must create the registry entry that is described in this section. You create the registry entry to enable the features that are introduced by the hotfix. Additionally, for this registry entry to take effect, all distribution groups that include users who have delivery restrictions must be flat. That is, the restricted distribution groups must not have nested distribution groups. The expansion logic will not work if the restricted distribution groups are nested.

The expansion logic that is introduced with the registry entry affects only restricted distribution groups. The expansion logic does not affect typical distribution groups. The expansion logic applies to delivery restriction checking on both mailboxes and connectors.

For distribution groups that are used in connector restrictions, we recommend that you set the registry entry on a connector bridgehead server that has no mailboxes. For Active Directory directory service user restrictions, if the restricted distribution groups have expansion servers, we recommend that you create the registry entry on the expansion servers.

To create the registry entry to enable the features that are introduced by the hotfix, follow these steps:

1. Click Start, click Run, type regedit, and then press ENTER.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeTransport
3. On the Edit menu, point to New, and then click Key
4. Type Parameters, and then press ENTER to name the new registry subkey.
5. Right-click Parameters, point to New, and then click DWORD Value.
6. Type RestrictionMethod, and then press ENTER to name the new registry entry.
7. Right-click RestrictionMethod, and then click Modify.
8. Type 2, and then press ENTER.
   
   Note When you set the value of the RestrictionMethod registry entry to 2, no restriction is applied to query-based distribution groups. In this case, messages are not filtered or delivered. If you set the value of the RestrictionMethod registry entry to 1, you can apply a restriction to query-based distribution group. However, this setting will not improve performance.
9. 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 Microsoft Exchange Server 2003 Service Pack 2.

To configure delivery restrictions on user mailboxes in Active Directory Users and Computers, follow these steps on the domain controller:

1. Click Start, point to Programs, point to Administrative Tools, and then click Active Directory Users and Computers.
2. Expand the Your_Domain container that contains the user accounts that you want to configure, and then click Users.
3. In the right pane, right-click User_Name, and then click Properties.
4. Click the Exchange General tab, and then click Delivery Restrictions.
5. In the Sending Message Size, Receiving Message Size, and Message Restrictions sections, configure the options according to your requirements.
6. Click OK two times.
7. Repeat steps 3 through 6 for any other users whose mailboxes you want to configure.
8. Quit Active Directory Users and Computers.

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base: