[otrs] Ticket Rejections and Replies

I'm a little confused about the the whole ticket rejection thing and which replies are sent, or if different circumstances result in different replies. First, there's the "Default rejection (Follow-up on closed ticket)", type "auto-reject" auto-response that would seem to do what the name suggests, yet a followup to a closed ticket seems to reopen it. Is this somehow time dependent and, if so, where is that configured. Then, there are the "PostMaster::PreFilterModule::NewTicketReject::..." entries in "Core::Postmaster", and filter rules that would result in tickets being rejected. So, which of these applies when and why? Any light anyone can shed on this would be greatly appreciated. John Blumel