You can export your contacts from Outlook.com and then import them into other email platforms like Gmail or Yahoo, or other versions of Outlook. Here's how:

• Sign in to Outlook.com
• Select  at the lower left corner of the page to go to the People page.
• On the toolbar, select Manage then choose Export contacts from the dropdown.

• Choose to export all contacts;
• Or choose only contacts from a specific folder,
• Select Export.
• At the bottom of the page, to save the file as "contacts.csv" in your default downloads folder, select Save. To modify the file name/location, select the arrow next to Save and select Save as.

Source: (https://support.office.com/en-gb/article/export-contacts-from-outlook-com-to-a-csv-file-578cca22-3550-4c73-b3f0-9978cfeac83f