Export Contacts and Email Addresses From Windows Mail
If you’ve built one address book in Windows Mail, you shouldn’t have to build that same address book again, even if you switch email programs or email services. You can export Windows contacts to a file format called CSV (comma-separated values), from which most other email programs and email services can import your contacts. To save your Windows Mail 8 and earlier contacts to a CSV file in Windows 8:
Export Contacts From the Windows 10 and Windows 11 People App
You can’t export your contacts located in the People app of a Windows 10 and Windows 11 computer to a CSV file. However, you can do this from your online Microsoft account and the online People app. From there, you choose Manage > Export Contacts to export the contacts to a CSV file. Go to the other email service and use the Import command to import your contacts to that service.
