Question : Lock Down TCP Port 25

I have an Exchange 2003 environment. ( Single domain, AD,Exchange on same box.)
I am experiencing repeat problems with internal users and trojan spamming,, outbound.
I would like to restrict  TCP Port 25. What is best recommended fashion to accomplish this task?

Answer : Lock Down TCP Port 25

OK, I think what you really want to say is you need help configuring antispam functionality. since email typically is accpeted from everyone you dont typicall restrict access to the port.

There are plenty of built in features in Exchange 2003 like  recipient filter, Rbl etc...
http://www.petri.co.il/block_spam_with_exchange_2003.htm