How do I refresh my email contact list in Outlook?

When you add recipients to an Outlook email message, you'll notice Outlook provides suggestions as you type. These suggestions are stored in the Auto-Complete List. You can refresh this list by either clearing a single saved contact or clearing the entire list. Then, the list will rebuild, adding contacts to the Auto-Complete List each time you send an email. If preferred, you can turn this feature off.

For instructions on how to remove a single saved contact, clear the entire list or disable the auto-complete feature, follow this Microsoft Guide.