1.Click on your "Contacts" or "Address Book."


2 Scroll through the list until you find a duplicate copy of an email address.
3 Right click on the duplicate and choose "Delete" or "Remove." Click "OK" or "Yes" to complete the removal.


Other than the above steps, I believe the only other way would be to use a 3rd party app. A google search will pull up many different programs.

I have experienced the same thing before; I suggest you can try using duplicate remover like Scrubly Duplicate Remover. This works well for me. I assure you this will end up you’re duplication’s problem.