An update is available that changes the format of SMTP messages from TNEF to S-TNEF

A software update is available that changes the format of SMTP messages that travel across a Microsoft Exchange 2000 Server Routing Group connector. The update changes the format from Transport Neutral Encapsulation Format (TNEF) to Summary TNEF (S-TNEF) format. S-TNEF is rendered in binary format.

Note Exchange 2000 Server must be running in native mode for this update to take effect.

By default, Exchange 2000 Server encodes outgoing SMTP messages that travel across a Routing Group connector in TNEF format. TNEF uses Base64 encoding. Base64 message encoding expansion can add approximately 33 percent to the message size.

When you send an e-mail message that contains an attachment across an Exchange 2000 Server Routing Group connector, you may receive a non-delivery report (NDR) that contains the following error message: The message encoding expansion that is associated with the Base64 format causes you to receive the NDR. You receive the NDR although the e-mail message is smaller than the current system limit.

Software update information

A supported feature that modifies the default behavior of the product is available from Microsoft. However, this feature is intended to modify only the behavior that this article describes. Apply this feature only to systems that specifically require it.

If the feature 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 feature.

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 feature. 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 feature is available. If you do not see your language, it is because the feature is not available for that language.

Prerequisites

This software update has the following prerequisites:

• You must be running Exchange 2000 Server in native mode for this update to take effect.
• You must be running Exchange 2000 Server Service Pack 3 (SP3). For additional information, click the following article numbers to view the articles 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-SP3 update rollup installed. For additional 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 your computer after you apply this update. However, Exchange services and Microsoft Internet Information Services (IIS) services are automatically stopped and then restarted when you apply this update.

Software update replacement information

This software update does not replace any other updates.

File information

The English version of this update 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.

How to apply the update

You must apply this update to Exchange 2000 Server mailbox servers and to Exchange 2000 Server bridgehead servers.