[vox-tech] spams originating from my friends server

[karthikeyan.balasubramanian]

Hi,

  One my friend has a server with some limited number of hosting.

  He is managing the whole server through CPanel.  Now he is getting
complaints from various people that lots of spam is coming from his 
server.  

  Now the question is 

1. How to trace which user is sending these spams?
2. How to stop it.  

Additional Info : 
Server Redhat 9.0
Mail Server : Exim
SMTP port is blocked already

  Any inputs are welcome.

Karthikeyan B