Well, I basically duplicated your procedure but could not duplicate the problem. I sent an email from Publisher 2003 to myself, at my main email account, and retrieved it with Outlook Express. Then, I forwarded that message to another email address of mine. It went out and then I retrieved it with Outlook Express. I had no problem forwarding the message or receiving the forwarded message.
You would normally not be forwarding one of these messages to your wife's computer, right? And, if you initially send all messages from Outlook and it displays properly at the client's end, is the issue you're raising really a problem? Perhaps you should find another computer, one at at different location, and do some addtional testing; you might ask one of your contacts to give you feedback or ask a friend or relative to verify that they could receive it in proper format.