Reply to Email and Start Discussion with email

Hi

I am having a couple of issues and also have some questions.... re email Parsing.

First Issue - I have been able to start a discussion bye sending an email to the Categories designated email, but I get no comment (the body of the email doesn't show up in the created discussion). any ideas ?
Second Issue - If I respond to an email that is sent as an update in a conversation(sent by system) no matter what I do it doesn't; show up in the discussion.. I have tried responding to the email it's sent form and the email set up for the category, also tried responding deleting everything in he subject except the code in the brackets e.g [#15]

Question: How do i get set up for each category to send out it's updates via the email associated with that category so that people can just simply reply to that email vs changing the email address.. Ihave some very simple users...

Thanks

NIck