Servers being used as email relays for spamming

[whipworks]

Hi,

I'm a bit puzzled onto how our server is being used as an email relay to send out spam. I've found one on the mail queue manager that there's this one email address based on Nigeria that is sending out a blast of email using our server. How does this happen and how do we stop this?

Thanks!

 

[cPanelMichael]

Hello

Could you post the message headers of one of the offending messages here so we can take a closer look? Ensure you post it in "CODE" tags and remove actual domain names and IP addresses.

Thank you.