Hi Yvonne, autoreplies will typically go to the "from" address, regardless of the "reply-to" address. I know this isn't very helpful, but that's what I've found in the past.
We have created some internal aliases from which we send emails, and then auto-replies don't clog up our inboxes. We have an intern review the auto-replies on a regular basis to see if people have left an organization, or other reasons for the auto-replies.