Outlook: Remove an Email Address from Autofill
Start a new email
Type the beginning of the email address you want to remove
Hover over the entry in the suggestions until it's highlighted
Click the X next to the entry or press the Delete key
Clear the entire auto-complete list by following these steps:
Open Outlook
Click the File tab
Click Options
In the Outlook Options window, click the Mail tab
Scroll down to Send Messages and click the Empty Auto-Complete List button
Click Yes when prompted to confirm
Click OK to close the Outlook Options window
Outlook remembers every address you type in the To, Cc, or Bcc fields. This can be problematic if the address is incorrect or outdated.