• Export your existing list from MailChimp. This will download a zip file that contains 3 files:
    • unsubscribed_members_export: Users that have used the link in the newsletter to unsubscribe
    • subscribed_member_export: Users that are subscribed to the mailing
    • cleaned_members_export: Users who’s email addresses have bounced and are no longer valid
  • Open your new list of email addresses in Excel
  • Filter and delete email addresses that appear in the unsubscribed_members_export and  cleaned_members_export files
  • Copy and paste the remaining email addresses into a new Excel spreadsheet
  • Copy and paste the email addresses from the subscribed_member_export
  • Data Sort by Ascending
  • In the data tab with columns selected click Remove Duplicates

Helpful Office article on Filter for unique values or remove duplicate values