When you email someone for the first time who is not in your address book using Microsoft Outlook, it saves it to a temporary file. With Outlook 2007 and 2010 it is easy to delete those individual email addresses from that drop down list so you do not accidently email that person again. This is very handy when you have someone with a new email address and you want to stop accidently emailing the wrong email address.
The procedure is simple. Start typing in the email address in a new email window as if you are going to email them. Their email address will appear in the drop down menu as you start typing. Simply click the X beside their email address to delete it and it’s gone. Or you can arrow down to highlight their name in the list and press delete on your keyboard. Now they will never show up in that list again and you will never accidently email them again.
This video below shows how easy it is to delete unwamted emails from Outlook 2010.