Hi Excellerant,
Well, the default way of attaching the XML should be sufficient. Your email VBA code that triggers will have to open the XML and query it, but you'd have to do a very similar thing if the email body was XML. So, I don't think you gain anything by switching the XML from the attachment to the email body. We've done Outlook VBA plugins that parse XML files attached to emails and do stuff with it. For an hour or two of time, we could share some code with you.
Good luck,
Patrick