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The msExchMaxIncomingConnections value has been changed from its default setting

[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: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool queries the Active Directory® directory service to determine the configured value for the msExchSmtpMaxIncomingConnections attribute of each SMTP virtual server.

By default, on an Exchange Server computer that is not part of a Microsoft Windows® Small Business Server 2003 installation, the msExchSmtpMaxIncomingConnections attribute is configured for an unlimited number of connections, as represented by a default value of 2000000000 for this attribute. On an Exchange Server computer that is a part of a Microsoft Windows Small Business Server 2003 installation, the default maximum number of incoming connections is 500.

The Exchange Server Analyzer also queries the Win32_OperatingSystem Windows Management Instrumentation (WMI) class to determine the value of the OSProductSuite key. The value of this key corresponds to a specific version of a Windows Server operating system.

If the Exchange Server Analyzer finds that the msExchSmtpMaxIncomingConnections attribute on an Exchange Server computer that is not part of a Microsoft Windows Small Business Server 2003 installation does not have a value of 2000000000, a non-default configuration message is displayed. The value of 2000000000 used for this attribute is both a theoretical limit, and the limit imposed on the user interface elements that let you configure this value.

Alternatively, if the Exchange Server Analyzer finds that the msExchSmtpMaxIncomingConnections attribute on an Exchange Server computer that is a part of a Microsoft Windows Small Business Server 2003 installation does not have a value of 500, a non-default configuration message is displayed.

From a security perspective, limiting the number of incoming connections may make sense. The capability of accepting an essentially unlimited number of incoming SMTP connections could lend itself to a denial of service situation. Too many simultaneous connections to the virtual server can overload your network and cause poor performance. Each organization should decide for itself what an appropriate value for this attribute is.

  1. Open Exchange System Manager.

  2. Expand Servers, 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 General:

    • To limit the number of incoming connections, select the Limit number of connections to check box and enter the value that you want.
    • To revert to the default of unlimited incoming connections, clear the Limit number of connections to check box.
  5. Click OK to save the changes.

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

 
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