outlook 2003

If I want to send a letter.
When I click on ?To? and type in the letter j I get a bunch of names as suggestions. I realize these are suggestions of recent addresses I have sent mail to in order to make it easier for me. The problem is some of these addresses are no longer valid or I don?t use them any longer and they keep coming up. How do I prevent this from happening? I love the feature but would just like to remove some of the addresses from this particular function.