Conflict between "reply to list" and "[listname]" in header?

I added an rc.local.s10 file to my list directory to add "[listname]" to the headers of all mailing list messages. That worked fine. Then in the rc.custom file, I uncommented "reply_to=$listaddr" and set it o "reply_to="Reply-To: $listaddr". That works, but now I've lost the "[listname]" in the message headers. Can anyone tell me what's going on? Thanks, Lu Rudolph