Outlook Rules Breaking Formatting

We have a daily weather e-mail that uses HTML as it's primary format.  It works fine for outside e-mails if you reply, send, forward, etc.  However, our user has set up an outlook inbox rule to automatically forward this e-mail.  It loses all formatting when it is forwarded by the Outlook inbox rule to outside e-mail addresses.  The inbox rule does not break formatting for us internally.  We tested this out on multiple accounts and they all do the same thing.  As long as it's not an inbox rule, the formatting stays and works for all e-mails.  We are using exchange.  Computers that receive the e-mail fine are all on the same network and all use the same exchange server.  It's outside e-mails that it breaks (gmail, aol, yahoo, etc).  What am I missing?