Real Issue Tracker

I am not sure how the issuetracker emails are parsed so that an email can be identified as either a new ticket or a followup on an existing one.

I see the ticket ID in the subject of sent messages. Myself and others frequently reply to tickets via email for a quick response, then follow up with more detail on the website. I usually delete the contents of the previous email when I reply to a ticket, so there isn't a ton of duplication. I usually instruct the client to do the same, so the threads aren't crazy long. Most of our clients create and respond to tickets via email, so this is kind of critical for us.

But when I send an email with only the subject containing the ticket ID it sees it as a new ticket, so it is not using the subject to determine if it is new or a reply.

Is there a way to make the parser identify the subject with the ticket id format? Or is there something we can specify in the body, so that we can instruct the users to include it in the replies. Most other mail enabled helpdesk systems only need to see something like "Ticket ID:xxx" in the subject to know it is an update not a new ticket. Ideally, it would be really helpful if a user could reply to a send to a friend email notification to reply.