Remove Duplicate eMails?

I have a list of around 1k emails some of them are duplicates and will be unable to go through entire list obviously due to so many emails.

Is there a way to sort through the emails and remove the duplicates on auto pilot, perhaps with a spreadsheet sofrware?

Many software can remove your duplicate emails such as Remove Duplicate Emails for Microsoft Office Outlook , Duplicate Email Remover, Outlook Duplicate Email Remove Software , Static Duplicated Email Finder, etc.

Go through what?

Where are the emails being stored? What software is being used?

Simply in notepad at the moment, however organizing and need to find a software that can handle this and instructions on how to do so. Emails will manually be inputed into the program, just curious if a spreadsheet like OpenOffice or Excell could perform the task?