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.
Want to Edit the Outlook Auto-Complete List?
For more control over Outlook's email address auto-complete file, try a tool like Ingressor.
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.
If the above doesn't work, you have to go "contacts" folder and modify accordingly.
REFERENCES
http://email.about.com/od/outlooktips/qt/et_del_autocomp.htm