Multiple SMTP port bindings configured

[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 whether the configured value for the msExchServerBindings attribute has been configured with multiple port bindings. By default, the msExchServerBindings attribute is configured for TCP port 25. If the Exchange Server Analyzer finds that the msExchServerBindings attribute has been configured with multiple port bindings, the Exchange Server Analyzer displays a non-default configuration message.

The msExchServerBindings attribute represents the TCP port on which the Simple Mail Transfer Protocol (SMTP) server listens for incoming connections. You can configure SMTP virtual servers to listen on one or more TCP ports. By default, all SMTP virtual servers are configured to listen on TCP port 25. You can change the SMTP listening port if you modify the rest of your internal messaging infrastructure accordingly. However, for SMTP virtual servers that accept messages directly from the Internet, you generally should use port 25 because SMTP servers on the Internet send messages through port 25.

Note that the Exchange Server Analyzer examines the value for the Exchange SMTP protocol virtual server. The Exchange SMTP protocol virtual server may or may not be the SMTP server that receives messages directly from the Internet. Some antivirus products and anti-spam products are designed to receive SMTP messages from the Internet on port 25 and to redirect to an Exchange SMTP virtual server on another port.

To view or modify the SMTP virtual server listening port

  1. In Exchange System Manager, expand Servers, expand an Exchange server, expand Protocols, and then expand SMTP.

  2. Right-click an SMTP virtual server, such as Default SMTP Virtual Server, and then click Properties.

  3. Select the General tab, and then click Advanced.

  4. A list of IP addresses and ports is displayed.

    • To change the existing port, select the IP address, and then click Edit.

    • To remove an existing port, select the IP address, and then click Remove.

  5. To save your changes, click OK, and then click OK to exit the Advanced dialog box.

  6. Click OK to close the Properties dialog box for the SMTP virtual server.

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