Windows 10 - Microsoft Outlook
Clear Email Address From Auto-Complete
Microsoft Outlook will automatically provide a list of email addresses as you type them in the To: field when composing an email. If you want to clear this list, follow these steps.
You can delete individual email addresses from the Auto-Complete list by typing the email address into the To: field when composing an email.
When the address appears, select the “X” next to it and it will be removed.