Stop email spamming attack on a server

Hello, I have a GoDaddy dedicated server hosting and the server is suddenly sending countless spam emails from a specific email address, I have changed the password of the specified email address, restricted sending emails of it from Cpanel, changed the entire server password and account password but it's not stopping it, I have tried reducing the sending per hour emails and it slowed it down but not stopped. I need a system administrator to go through the server, and reconfigure it, and edit the server configuration to stop all possible spam emails with exe, and other weird compressed files attachments. my budget is 15$ for the project, thanks.