The Mail app uses the People app for Windows 10 to store contact information. While you cannot directly export your contacts from the People app, you can export your contacts from Outlook.com to a CSV file and then import them back and/or import them into other email apps such as Gmail or Yahoo, or other versions of Outlook. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.