How to change SMTP port 25 to another port in Microsoft Exchange Server

This article explains how to change Simple Mail Transport Protocol (SMTP) port 25 to another port in Microsoft Exchange 2000 Server or in Microsoft Exchange Server 2003 or in later versions.

SMTP is the default protocol that Exchange 2000, Exchange 2003, Exchange Server 2007, or Exchange Server 2010 uses to communicate between Exchange-based servers within one site or between a server and the Internet. Therefore, if you change the port that is used to listen to SMTP traffic, you may experience wide-ranging and unexpected negative effects. When you change the default port configuration, you should carefully consider and test the configuration before you implement it in a production environment.

How to Change the SMTP Listening Port

To change the SMTP listening port on a server that is running Exchange 2000 or Exchange 2003 from port 25 to another port, for example, port 26, follow these steps:

1. Start the Exchange System Manager.
2. Locate and click Servername, click Protocols, and then click SMTP.
3. Right-click the Default SMTP Virtual Server object, and then click Properties.
4. On the General tab, click the Advanced button, click the Edit button, and then set the Transmission Control Protocol (TCP) port to 26 (or whatever new value you require).

This method sets the port that this virtual server listens to for SMTP traffic.

Warning If you change this port number, the virtual server will not be reachable by other SMTP virtual servers that are configured to have the default (Outgoing) SMTP port 25.

How to Change the Outbound TCP Port

NOTE: Every remote SMTP server that you want to communicate with must be configured to accept connections on the specified port. In most cases, you do not want to change the default port setting.

To change the outbound TCP port, follow these steps:

1. Start the Exchange System Manager.
2. Locate and click Servername, click Protocols, and then click SMTP.
3. Right-click the Default SMTP Virtual Server object, and then click Properties.
4. Click the Delivery tab, and click the Outbound connections button. Set the TCP port to 26 (or whatever value you require).
5. Quit the Exchange System Manager for the changes to take place.

All outbound SMTP traffic is now sent to port 26 on other servers.

NOTE: For these steps, the Display routing groups check box is enabled on the Exchange Organization Name properties in a mixed mode site.
To change the SMTP port on a server that is running Exchange 2007 or Exchange 2010, follow these steps:

1. Open the Exchange Management console.
2. Expand Server Configuration, and then highlight on the Hub Transport option.
3. In the middle pane highlight the HUB server that you want to change.
4. In the bottom pane right-click on the receive connector that you want to change the port number for and then click Properties.
5. On the Network tab and in the top pane select the IPV4 or IPV6 and then click Edit.
6. Type the desired port number in the provided location and select OK