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The msExchSmtpMaxOutgoingConnections value has been altered from its default of 1000

[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 msExchSmtpMaxOutgoingConnections attribute has been altered from the default value of 1000. By default, the msExchSmtpMaxOutgoingConnections attribute is configured for a maximum of 1000 outbound Simple Mail Transfer Protocol (SMTP) connections. If the Exchange Server Analyzer finds that this attribute does not have a value of 1000, a non-default configuration message is displayed.

The msExchSmtpMaxOutgoingConnections attribute represents the maximum number of outbound connections that can be made by an SMTP virtual server on the Exchange server.

Generally, there is no best practices recommendation for determining the correct value for this attribute. Each organization must determine for itself 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 make extensive use of 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 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 msExchSmtpMaxOutgoingConnections attribute is listed in the Limit number of connections to field. Change this field as needed, and then 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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