Linux Server QMail and PHP problems. Server compromised

Linux Server has been compromised and appears is being used as a mail rely causing our server to overload and impact customers. We require an experienced person to determinre the source of the problem on the server, fix the problem and implement measures to prevent future similar threats. There are approximatley 70 sites hosted on this server which will be relocated to a new server, but we will need them to be clean prior to migration. This is a job for an experienced admin who will minimise further down time to the server in question and highlight areas that require attention moving forward. Assistance with server spam configuratin will aslo be required. This does require immediate attention so please do not accept this job if you are unavailable to commence quickly.