Removing Duplicate Email Addresses in an Address Book

After searching for a free easy program to do this for me, a Mozilla Thunderbird user, I decided the best way is to use Excel, like this:

First, export the address book to *.csv comma-separated format.

From: http://office.microsoft.com/en-us/excel/HA010346261033.aspx

Open the file in Excel. Select all of it. Do DATA then FILTER, then ADVANCED FILTER, then check off UNIQUE RECORDS ONLY. That will show only the unique records. Then COPY what is showing to the clipboard. Go back to DATA then FILTER then ADVANCED FILTER then Do NOT check off UNIQUE RECORDS ONLY. Then the whole file will show. Press the DELETE key to delete all the rows. Then do CTRL-V to paste in the uniquely filtered rows. Then SAVE the file, and all the duplicates will be gone. Then import the *.cxv file back into the email address book.

There isn't a way I know of to filter on just duplicates in one column and deleting all rows that have duplicates in that column even if they are different in other columns.

This and other Mozilla tips are at: http://rasmusen.org/a/mozilla-rasmusen.txt