A user who is connected to an Exchange 2003 front-end server by using an IMAP4 e-mail client program may be unexpectedly disconnected from the session

When you have Microsoft Exchange Server 2003 configured in a front-end/back-end server environment, you may experience the following problem. A user who is connected to the Exchange 2003 front-end server by using an Internet Message Access Protocol, Version 4rev1 (IMAP4) e-mail client program may be unexpectedly disconnected from the session. When this problem occurs, the user may receive an error message that is similar to the following:If this user connects directly to the Exchange 2003 back-end server by using the IMAP4 e-mail client program, the user is not disconnected from the session.

This problem may occur if the following conditions are true:

• One or more of the e-mail messages that the user tries to retrieve contain a large header.
  
  Note An e-mail message may have a large header if it has been forwarded many times.
• The IMAP4 client program performs a FETCH BODYSTRUCTURE operation or a FETCH BODY operation to parse the e-mail message that contains a large header.

This problem occurs because Exchange 2003 limits the number of embedded MIME message levels that can be processed in an e-mail message. Currently, this limit is 32 levels.

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 be running Microsoft Exchange Server 2003 Service Pack 1 (SP1) to install this hotfix. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Restart requirement

You do not have to restart your computer after you apply this hotfix. However, many Exchange-related services are automatically stopped and then restarted when you apply 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 tool in Control Panel.

Hotfix installation information

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

After you install this hotfix, you can use the following new registry value to modify the number of MIME message levels that can be processed in an e-mail message in Exchange 2003: By default, Exchange 2003 permits 32 MIME message levels to be processed in an e-mail message. You can use this registry value to increase this limit to 256 levels.

Installation notes

• This hotfix is intended for installation on your Exchange 2003 front-end servers. You do not have to install this hotfix on your Exchange 2003 back-end servers.
• The LimitNestingLevels registry value also affects messages that are encoded by using Transport Neutral Encapsulation Format (TNEF), and it affects I-Mail conversion on your Exchange server.

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.

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