We do exactly what you want with virtually all email sent out.
The only problem is the complexity associated with the email client that you use. If you are using a web-based closed, it should be a snap. If you are using Lotus Notes, then you must process the message in the Domino server to create a hotspot before the email is forwarded to the recipient. In Outlook, I think - but do not know for sure - that it works without too much trouble.