We run a SBS 2003 server running exchange 2003.We want to be able to change the default port from port 25 to another suitable port.We want to do this to prevent any virused machine that are connected to the network from being able to send email(spam) out as we are keep getting black listed.I understand to do this we will need to block port 25 on our router and open another port but what we are not sure about is how to change the port exchange uses.Look forward to your repliesThanks in advanceThanks in Advance

Change the port on the SMTP virtual server. Start the Exchange System Manager, Servername, click Protocols, and then click SMTP, Right-click the Default SMTP Virtual Server object, and then click Properties , 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).http://support.microsoft.com/kb/274842Raj

Hi, Secure your Exchange 2003 SP2 by doing some configuration changes so that we can avoid internal threat to outside as well vice-versa please check the below links to harden your Exchange 2003. http://www.petri.co.il/block_spam_with_exchange_2003.htm http://www.petri.co.il/block_spam_with_exchange2003_imf.htm http://www.amset.info/exchange/imf.asp use the RBL's mentioned in the below article to put in Exchange 2003 http://www.spamblogging.com/archives/000138.html You cannot block port 25 on router level since Public mail servers send mails only on port 25, if you block 25 at router level you cant receive external mails. If you want to change the port on exchange2003 use ISA server or any perimeter level spam devices.Hari Bylapudi

As Rajnish has already linked the KB to change the outbound SMTP port you can follow it for sure and now that you are not using port 25 anymore you can block the outbound connections on your firewall or router. What you can not block is the inbound traffic on port 25. This will stop all the mail flow from outside world.Milind Naphade | MCTS:M (Exchange 2007 and 2010) | http://www.msexchangegeek.com