Due to faulty antivirus applications that interfere with the process of receiving and sending emails.

As a result of malfunctioning hardware or Outlook add-ins and programs.

After switching from other email programs to Outlook.

When you merge PST data files, mailboxes, or Outlook folders.

If you transfer email messages or entire mailboxes to another computer.

After Microsoft Office or Windows updates.

If you receive mail multiple times because of connection errors or incorrect settings.As a result of the Outlook rules not working properly.After synchronization failures or connection errors with the mail server.Due to errors when manually copying Outlook messages.After importing data or restoring emails from a backup archive.In what cases do duplicate emails appear in Outlook? You can delete the marked duplicates or move them to another folder by yourself or using another utility for automatically removing duplicated Outlook messages.

This process is also completely secure, as it simply marks duplicate messages rather than remove them. This utility will automatically find duplicate Outlook emails and assign them a category, flag them, or set an expiration date.

Delete duplicates in outlook archive