This only let's me know it the massage has been received or read; I want to be able to see the emails that I've sent, that no one replied to. For instance being able to generate a list of all the emails that I've sent, that I never got a reply to. When you, like I, send 60 - 80 mails per day, it would be be nice to be able to say "Hey Bob, I sent you an email 5 days ago, who come you haven't answered", without having to do some serious digging.

Any more ideas?