Rated 5 out of 5 stars
Great Addon. I've been using it for roughly 4 years and it saves me a lot of hassle. When I forward an email often people reply to me and not the attached forwarded email and this addon helps me avoid the confusion entirely.
I got version 0.7.6.1 from http://mailredirect.mozdev.org/
and it has since automatically updated itself to version 0.7.6.2 :-P