Fix Duplicate Thunderbird Address Book Contacts

For the longest time, I’ve been annoyed with Thunderbird because it doesn’t catch duplicate contacts as you enter them into your address book. This seems like a standard thing to check for, but even in the latest release, this still hasn’t been fixed.

This was really starting to get out of control for me, so I did some thinking today about how to fix it, and finally came up with an answer. There is an add-on that’s supposed to do this, but it hasn’t been updated in years, and doesn’t work on the latest version.

So here’s the process that worked for me:

• Open your address book, and select the address book that you wish to de-duplicate
• Go to Tools > Export, and export the address book as a CSV file.
• Open that file in OpenOffice Spreadsheet, and sort it by the column called “Display Name”
• Insert a column to the left (or right, whatever) of the “Display Name” column, and fill it with entries such as =if(C2=C3, "Duplicate", "OK") Where C corresponds with the column in which you’re looking for duplicates. Fill the entire column with such entries all the way to the bottom.
• Next, visually look for duplicates and delete them. Once that’s done, do the same thing for the email address column, and you should be able to eliminate all the duplicates.
• To get them back into Thunderbird, go to Tools > Import, and import the file. This will create a new address book by the name of the file.
• From there, simply delete your old address book, and rename the new one to something useful.

All done!