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SMTP configuration warning

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2006-05-03

The Microsoft® Exchange Server Analyzer Tool queries the Active Directory® directory service to determine whether the value for the msExchSmtpMaxMessageSize.attribute has been changed from the default value of 0. By default, the msExchSmtpMaxMessageSize attribute is configured for unlimited message size.

The Exchange Server Analyzer displays a warning if the following conditions exist:

  • The msExchSmtpMaxMessageSize attribute does not have a value of 0.

  • Exchange is not running on Microsoft Windows® Small Business Server 2003.

The msExchSmtpMaxMessageSize attribute represents the maximum size of each SMTP message that can be sent or received. From a security perspective, it is a best practice to limit the maximum size of SMTP messages that can be sent to and received from the Internet. However, for internal SMTP messages, such as those that travel between Exchange servers in the same organization, it is recommended that you leave the msExchSmtpMaxMessageSize attribute set to 0.

Internally, Exchange uses SMTP messages to handle tasks such as public folder replication. If the msExchSmtpMaxMessageSize attribute is configured to have too low a limit, this limit could cause public folder replication problems and other intra-organizational message delivery failures.

If this Exchange server is a bridgehead server that transfers SMTP messages to and from the Internet, you may be able to safely ignore this warning. If this Exchange server handles internal SMTP messages, you should change the value for the msExchSmtpMaxMessageSize attribute back to its default setting of 0.

noteNote:
If you set the message size limit too low, it could prevent offline address book replication between Exchange Server computers. For more information, see Microsoft Knowledge Base article 326154, "You cannot download the offline address book in Microsoft Outlook in Exchange 2000 Server" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=326154).
To view and configure the maximum SMTP message size
  1. In Exchange System Manager, expand Servers, expand an Exchange server, expand Protocols, and then expand SMTP.

  2. Right-click an SMTP virtual server, for example, Default SMTP Virtual Server, and then select Properties.

  3. Select the Messages tab.

  4. To revert to the default setting of 0, clear the Limit message size to (KB) check box. Alternatively, leave this box checked and configure any value that you want.

  5. Click OK to save the changes and to close the Properties dialog box of the SMTP virtual server.

For more information about SMTP virtual server settings, see the following Microsoft Knowledge Base articles:

 
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