Which address out of the reply-to and from address field recieves the bounce-backs and out of office replies?
Neither would receive the bounce backs in most cases. Those should be going to the return-path, which if you're sending through Campaign Monitor would be coming back to us to be processed and put into your reports. The out of office replies are a bit trickier though. It's really up to the incoming mail server or email client and outside of your control. Sometimes they send to the reply-to address and sometimes they ignore it and send to the from address. If you want to ignore them all your best bet is to set up filters for both addresses (assuming they're different) to just send anything with those typical out of office subject lines to the trash or to a specific folder to be dealt with.