Stop my VPS server from spamming?

Hi,
I have a VPS server and one of my accounts has been compromised.
I am still trying to find the code that allows for upload of these spamming files but for now I have just terminated the account on the server.

Just wondering if there is a setting I can change in WHM/CPANEL that will stop emails being sent with fake headers, perhaps only allowing headers from account on my VPS?

mail() on [/home/mywebsite/public_html/mail.php(586) : eval()'d code(2) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code(1) : eval()'d code:185]: To: random_email@yahoo.com.au -- Headers: From: Apple Inc <secure@service.com>  MIME-Version: 1.0  Content-Type: text/html

Thanks.