ionice every imap process automatically

I want to ionice a process on its startup. In our hosting environment, we use old Paralells Confixx servers. (Yes I know, Confixx is outdated, but that is not the question). We use courier for mails and sometimes it happens, that the /usr/bin/imap Maildir process eats up the whole I/O which also causes high CPU load. We allways manually ioniced (ionice –c 3 –p [PID] ) the process and the I/O went down. What is the best way to automatically ionice every imap process? I’m not very experienced in the courier mail server.