Remove Malicious Mailer and Repair Postfix - Linux Centos

Hello I am Paul a PHP / Mysql developer. I had a issue with a malicious script sending emails on my server. I upgraded to a server with newer version of plesk / linux and moved everything over. the email system was working for a while and then stopped sending mail and I found some of the spam from the original server in the queue. Not sure if this was brought over using plesk migration manager. I need my email system working POSTFIX on new server (Php scripts are not sending mail) and I need the malicious mail sender located and removed. Please email me your approach on figuring out why Email has suddenly stopped and where the malicious code is originating Thank you Paul PS here is info on the attached file from original server malicious script found--- We killed these malicious processes, but made sure to store what files they were using at /root/malware_lsof.txt. Your IT administrators can use this for further investigations. The vulnerability is most probably in the code of your website, but the outdated Plesk Panel cannot be ruled out.