Back up New Outlook data

You can use the procedure described in https://support.microsoft.com/en-us/outlook/people/import-or-export-contacts-in-outlook-using-a-csv-file

Export contacts to a .csv file in new Outlook

When you export your contacts from new Outlook, a copy of your contacts is saved to a CSV file. You can then use this file to import your contacts to another email account.

1. On the side panel select  People.
2. From the ribbon, select Export contacts. 
3. In the dropdown under Contacts from this folder, choose an option then select Export.
4. The exported .csv file is saved to your Downloads folder.

Import contacts to new Outlook using a .csv file

Use a comma separated values file (CSV) to import your contacts into your Outlook account.

Tip

For best results, make sure that the CSV file has UTF-8 encoding. This encoding works for all languages and alphabets.

In new Outlook, from the navigation bar, select  People.

Tip

If People aren't already in the left navigation bar, select More apps, then People to add it. After adding People, right-click and select Pin to keep it in the left navigation bar.

From the ribbon, select Import contacts. 

Select Browse, choose your CSV file, and select Open.

Select Import.

Note

If the file doesn't have UTF-8 encoding, the import tool may not recognize and display all text correctly. The import tool will then show you some example contacts from your file, and you can check that the text is readable and correct. If the text is not displayed correctly, select Cancel. You will need a file in UTF-8 encoding to continue. Convert your CSV file to use UTF-8 encoding and restart the import. To learn more about UTF-8 encoding, go to Why should I care about UTF-8 encoding?

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hth

Marcin