DupeX Description:

DupeX is an easy-to-use application that will let you quickly find (and remove) duplicate email addresses from a mailing list. If you manage a large mailing list, it can help remove duplicates and keep your list pristine. A simple step-by-step interface lets you select a text file containing the addresses. DupeX will scan the file and report on duplicates found, letting you save (in plain-text or comma-separated format) both the unique addresses and the duplicates. It can also combine multiple e-mail lists into one "clean" file (again in text or CSV format) and giving you the option of saving the duplicates to another file.