When typing an e-mail address into the "To/Cc/Bcc" fields, Outlook will supply a list of e-mail address that are similar to what your are entering. The list could be rather long if you have some e-mail address in the list that are no longer working e-mail address. You can delete some of the auto complete entries in just a few simple steps. This will also bel useful if someone in your contact list has changed, companies and you no longer need to send e-mails to their old e-mail address. This feature is available in Outlook 2010, Outlook 2007, and Outlook 2003.