Outlook remembers every address you have typed in a To:, Cc: or Bcc: field. This is good: when you start keying in a name or address, Outlook automatically suggest the contact in its entirety.
Unfortunately, Outlook remembers the mistyped and old as well as the correct and current — and suggest it indiscriminately. Fortunately, getting rid of entries you no longer want to appear in the auto-complete list is easy.
Delete an Address from the Outlook Auto-Complete List
To remove a name or email address from Outlook’s auto-complete list:
- Create a new email message in Outlook.
- Start typing the name or address you want to remove.
- Use the down arrow key to highlight the desired (undesired) entry.
- Press Del.
Prevent Outlook Address Auto-Completion Altogether
You can also stop Outlook from suggesting email addresses as you type:
- Select Tools | Options… from the menu.
- Go to the Preferences tab.
- Click E-mail Options….
- Now click Advanced E-mail Options….
- Make sure Suggest names while completing To, Cc, and Bcc fields is not checked.
- Click OK.
- Click OK again.
- Click OK once more.
This article taken from : http://email.about.com/od/outlooktips/qt/et_del_autocomp.htm thanks to Heinz Tschabitscher, About.com Guide
