The msExchSmtpMaxSessionSize value has been altered from its default of 0

[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]  

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool queries the Active Directory® directory service to determine if the configured value for the msExchSmtpMaxSessionSize attribute has been altered from the default value of 0. By default, the msExchSmtpMaxSessionSize attribute is configured for unlimited message size. If the Exchange Server Analyzer finds that this attribute does not have a value of 0, a warning message is displayed.

The msExchSmtpMaxSessionSize attribute represents the maximum amount of data in kilobytes (KB) that will be accepted for each SMTP session. From a security perspective, limiting the size of SMTP sessions for messages sent to and received from the Internet is a best practice. However, for internal SMTP sessions, such as those between Exchange servers in the same organization, it is recommended that you leave the msExchSmtpMaxSessionSize attribute set at 0.

Internally, Exchange uses SMTP messages to handle tasks such as public folder replication. If the msExchSmtpMaxSessionSize attribute is configured with too low a limit, it 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 can safely ignore this warning. If this Exchange server handles internal SMTP messages, you should change the value for the msExchSmtpMaxSessionSize attribute back to its default setting of 0.

  1. Open Exchange System Manager.

  2. Expand Servers, then expand an Exchange server, expand Protocols, and then expand SMTP.

  3. Right-click an SMTP virtual server (for example, default SMTP virtual server) and then click Properties.

  4. Click Messages.

  5. To revert to the default setting of 0, clear the Limit session size to (KB) check box. Alternatively, leave this box checked and configure any desired value.

  6. 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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