Forwarding HTML email changes to plain text

We have an HTML formatted email that we send out from one of our systems to a GroupWise 2012 mailbox. That mailbox has a rule to forward the message to a distribution list. When we set it up to forward, the message is converted to plain text for the recipients. The only way to preserve the HTML formatting is to forward as an attachment. Is there a way to fix the forward rule so we don't have to use the attachment option?

Server: GW2012 SP2