Doesn't an easy "unsubscribe" method, coupled with a "you're getting this because you asked" note in the text -- usually fix that?
I think that systems have matured.
It's the users who haven't.
I think at the
very least, MA3 should display a message after 30 days indicating that this version is "rather old" and they should check to see if there is an update. I am absolutely convinced that 80% of MA3 users will be running "3.0" 2 years from now, completely unaware of all the things Jim will be adding during that time.