Can I use htmlmail.tpl.php to set 'reply to'?

I'm trying to get Drupal with the Subscriptions and Mailhandler modules to behave like a listserv.
Mailhandler lets me post to a content type on the site using a listserv@mydomain.org email.
Subscriptions lets me send that post back out to subscribers.
The problem is that the email is sent to subscribers from webmaster@mydomain.org
I need it to be sent from listserv@mydomain.org or set the reply to field to that email in this circumstance.
Can a custom htmlmail.tpl.php help me to do this?
Any other thoughts?

Thanks