[iBook] Deleting unwanted Mail addresses

[gooddog at interlync.com]

Folks;

I have totally forgotten how to get rid of unwanted old email  
addresses from appearing in the TO field in Mail. They exist  
somewhere, but I can't seem to get rid of them. I used to know how to  
do this, but have lost that part of my brain along the way.

Can someone clue me in?

Thanks in advance.