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The msExchSmtpMaxOutgoingConnectionsPerDomain value has been changed from its default of 100

[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 whether the configured value for the msExchSmtpMaxOutgoingConnectionsPerDomain attribute has been changed from the default setting. The msExchSmtpMaxOutgoingConnectionsPerDomain attribute represents the maximum number of outbound connections per domain that can be made by an SMTP virtual server on the Microsoft Exchange server. By default, on an Exchange Server computer that is not part of a Microsoft Windows® Small Business Server 2003 installation, the msExchSmtpMaxOutgoingConnectionsPerDomain attribute is configured with a default value of 100. On an Exchange Server computer that is a part of a Windows Small Business Server 2003 installation, the default maximum number of outgoing connections per domain is 10.

The Exchange Server Analyzer also queries the Win32_OperatingSystem Windows Management Instrumentation (WMI) class to determine the value if 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 msExchSmtpMaxOutgoingConnectionsPerDomain attribute on an Exchange Server computer that is not part of a Windows Small Business Server 2003 installation does not have a value of 500, a non-default configuration message is displayed.

Alternatively, if the Exchange Server Analyzer finds that the msExchSmtpMaxOutgoingConnectionsPerDomain 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 10, a non-default configuration message is displayed.

Generally, there is no best practices recommendation for determining the correct value for this attribute. Each organization needs to determine the appropriate value to set. That said, the default value may be too high for some organizations. You can monitor and determine the actual number of SMTP outbound connections made by an Exchange SMTP virtual server by collecting the following performance counters on your Exchange server:

 

Object | Counter Explanation

SMTP Server | Outbound Connections Current

The number of connections currently outbound.

SMTP Server | Outbound Connections Total

The total number of outbound connections attempted.

If your organization does not extensively use outgoing SMTP on this Exchange server, consider lowering the value for this attribute. Lowering the maximum number of simultaneous outbound SMTP connections that can be made at any given time could potentially slow any spikes in SMTP server activity that may be caused by incorrect configuration, innocent mistake, malicious activity, a message loop or other malfunction, or a virus outbreak or security breach.

  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 Delivery, and then click Outbound Connections.

  5. The current value for the msExchSmtpMaxOutgoingConnectionsPerDomain attribute is listed in the Limit number of connections per domain to field. Change this field as you want and click OK to save your changes. Accepted values for this field include any whole number between 1 and 1999999999.

  6. Click OK 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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