Hi Bruce,
Are these duplicate contacts created in a separate contacts folder or in the same contacts folder?
Do you have your email account synced on other devices, especially mobile devices? This issue usually happens because the same account was synced on a mobile device. You may try to stop syncing your accounts with any mobile device and then see whether there
are more duplicate contacts get created.
To delete these duplicate contacts, you may try the steps in this article:
https://support.office.com/en-us/article/resolve-or-delete-duplicate-contacts-0fa9c0a0-499a-48ab-b818-4e6463ccb9fa
Hope this helps.
Regards,
Steve Fan
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