There may come a time when Outlook will send multiple copies of the same message. These duplicate messages will all be marked as unread and appear multiple times in your Inbox. This issue typically happens when your Outlook profile gets corrupted.

In cases such as this, you can repair your Outlook profile. Repairing your Outlook profile will look for and fix errors in the profile.

Learn more about Outlook sending multiple copies of emails.

For further information, please check with Outlook support.