Redmine

All, we have a mailbox that gets imported into a Redmine tracker to create new issues. However, if the user or someone else CC'd on the original message replies, a whole new issue is created.
We are currently using a cron job such as the following to import the messages as issues:
/usr/bin/rake -f /var/redmine/Rakefile redmine:email:receive_imap unknown_user=accept no_permission_check=1 RAILS_ENV=production host=imap.gmail.com port=993 username=<removed> password=<removed> ssl=1 project=ivr tracker=support

I know that redmine will append if the reply include the ticket number, however, I was wondering if it would be possible to have redmine append if the original subject matches and the issue is still open.

Thank you in advance for any assistance.

Jes