In a Microsoft Exchange 2000 Server organization, some e-mail messages are not delivered when an e-mail message is sent from the Internet to multiple Exchange 2000 recipients

In a Microsoft Exchange 2000 Server organization, some e-mail messages are not delivered when an e-mail message is sent from the Internet to multiple Exchange 2000 recipients. The first recipient receives the message, but the other recipients may not.

When this problem occurs, the following Information event is logged in the Application log for each recipient who did not receive the message:

Event ID: 9537
Type: Information
Source: MSExchangeIS Mailbox Store
Category: Transport Delivering
Description:
A duplicate message arrived on database "Storage_Group\Mailbox_Store". Ignoring delivery of message (Internet Message Id=<message_ID>) to /o=Organization/ou=Administrative_Group/cn=Recipients/cn=username.

This problem may occur if the following conditions are true:

�	The message is originally sent from the Internet to multiple Exchange 2000 recipients.
�	The message contains a very long Message ID field in the Simple Mail Transfer Protocol (SMTP) header. Because of the Message ID field length, the combination of the Message ID field and the Submit Time field is over 255 bytes.

In this case, the Exchange store delivers the e-mail message to the first recipient. However, the Exchange store incorrectly detects the other instances of the message as duplicates. Therefore, the Exchange store discards the other instances of the message.

Hotfix information

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Microsoft Exchange Server 2003 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

This hotfix has the following prerequisites:

�	You must be running Microsoft Exchange 2000 Server Service Pack 3 (SP3). For more information about how to obtain the latest Exchange 2000 service pack, click the following article number to view the article in the Microsoft Knowledge Base: 301378 How to obtain the latest Exchange 2000 Server service pack
�	You must have the August 2004 Exchange 2000 Server post-Service Pack 3 update rollup installed. For more information, click the following article number to view the article in the Microsoft Knowledge Base: 870540 Availability of the August 2004 Exchange 2000 Server post-Service Pack 3 update rollup

Restart requirement

You do not have to restart the computer after you install this hotfix. However, the following Microsoft Exchange services are automatically stopped and then restarted during the hotfix installation:

�	Microsoft Exchange POP3
�	Microsoft Exchange Event
�	Microsoft Exchange IMAP4
�	Microsoft Exchange Information Store

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 tool in Control Panel.

   Date         Time   Version            Size    File name
   ---------------------------------------------------------
   13-Sep-2004  04:47  6.0.6617.6      2,310,144  Mdbmsg.dll
   12-Sep-2004  05:02  6.0.6617.6      4,685,824  Store.exe
				

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

When you install this hotfix, the Disable Duplicate Detection Over 255 bytes value is added to the registry. By default, this registry value is disabled. After you install the hotfix, you must change the setting of the Disable Duplicate Detection Over 255 bytes value to 1 to enable the hotfix.

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.

To enable the hotfix for the private store, follow these steps:

1.	Click Start, click Run, type regedit, and then click OK.
2.	Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersPrivate
3.	Right-click Disable Duplicate Detection Over 255 bytes, and then click Modify.
4.	In the Value data box, type a value of 1 to enable the hotfix, and then click OK. Note To disable the value and to return Exchange 2000 to its default behavior, type a value of 0 in the Value data box, and then click OK.
5.	Quit Registry Editor.

To enable the hotfix for the public store, follow these steps:

1.	Click Start, click Run, type regedit, and then click OK.
2.	Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersPublic
3.	Right-click Disable Duplicate Detection Over 255 bytes, and then click Modify.
4.	In the Value data box, type a value of 1 to enable the hotfix, and then click OK. Note To disable the value and to return Exchange 2000 to its default behavior, type a value of 0 in the Value data box, and then click OK.
5.	Quit Registry Editor.

After you enable the hotfix, if a message is received in which the combination of the Message ID field and the Submit Time field is over 255 bytes, the following event is logged:

Event ID: 2093
Type: Information
Category: Transport Delivering
Description:
Duplicate detection for the message has been skipped because the Internet Message ID is too long and the administrator has set the Disable Duplicate Detection Over 255 bytes registry value. The recipient may get duplicates of this message.

Sender E-mail Address: sender_e-mail_address
Internet Message ID: message_ID

If the registry entry is disabled, and if a message is received in which the combination of the Message ID field and the Submit Time field is over 255 bytes, the following event is logged:

Event ID: 2094
Type: Information
Category: Transport Delivering
Description:
The length of the Internet Message ID for this message is greater than that which duplicate detection can handle. The message was discarded. Please set the registry value [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersPrivate_or_ParametersPublic] DWORD "Disable Duplicate Detection Over 255 bytes" to change this behavior.

Sender E-mail Address: sender_e-mail_address
Internet Message ID: message_ID

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