[otrs] compose answer: cc-field is auto-filled ??

Hi, I have a few OTRS installations (2.2.5) and with two I have a strange problem: when I answer a ticket by using one of the "compose answer" links I have, the CC field of the ticket is auto-filled with the original "TO" email address. (so when the agent do not pay attention and not clear the cc field, the answer ticket is sent to the queue again...) I'm very confused about this and researched all the config options, but I can not find any option to control this. anyone??? regards, Peter van Beugen