Messages in the deferred delivery queue cause performance problems on an Exchange 2000 or Exchange 2003 computer

Computers that are running Microsoft Exchange 2000 Server or Microsoft Exchange Server 2003 may experience high CPU utilization when the deferred delivery queue is full of deferred messages.

This problem may occur when the following conditions are true:

• Many messages are sent to users who have been disabled by deleting the msExchMasterAccountSID attribute.
• The Exchange 2000 deferred delivery queue is full of deferred messages.

For example, when a message that cannot be delivered is added to the deferred delivery queue, the message is not removed from the deferred delivery queue until its scheduled delivery time. If the message still cannot be delivered at its scheduled delivery time, the message cycles through the deferred delivery queue until you manually delete the message from the queue. When the deferred delivery queue is active and contains many messages that cannot be delivered, there can be a significant performance impact.

When many messages are sent to users who are no longer mailbox-enabled, the messages are deferred every half hour and can accumulate in large numbers. The messages are constantly cycled through the information store and back to the deferred delivery queue.

The following conditions can cause messages to accumulate in the deferred delivery queue:

• A message is sent to a users mailbox while the mailbox is being moved.
• The msExchMasterAccountSID attribute for a mailbox-enabled user is deleted.

Exchange Server 2003

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

To resolve this problem, obtain the August 2004 Exchange 2000 Server Post-Service Pack 3 update rollup.

Exchange 2000 Server

For additional information, click the following article number to view the article in the Microsoft Knowledge Base: Component: TRANSPORT CORE

The English version of this hotfix has the file attributes (or later) 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 tool in Control Panel.
Note Because of file dependencies, this hotfix requires Microsoft Exchange 2000 Server Service Pack 3 (SP3). For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

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.