Remove Duplicate Address Book Entries in Thunderbird

Martin Brinkmann
Dec 6, 2007
Updated • Mar 3, 2014
Email, Thunderbird

It can happen that you end up with duplicate address book entries in Mozilla Thunderbird and wonder how you can remove them so that only one entry per contact is visible in the Thunderbird Address Book.

The current Thunderbird address book is most likely fragmented or corrupt,  and the easiest way to fix that is to create a new Address Book and copy the contents of the old Address Book into the new one.

You should backup your Thunderbird profile before you start this process. The easiest way would be to use the software MozBackup which creates a backup of a selected profile with just a few clicks.

After the profile data has been saved you can begin the process of creating a new Address Book in Thunderbird to get rid of Duplicate Address Book entries.

find manage duplicates

  • Click on Tools > Address Book which opens the Address Bock. Click now on File > New Address Book and enter a new name for it. This is only temporary, so a name like 'temp address book' would do
  • Click on an entry in your old Address Book, use the shortcut CTRL + A to mark all entries
  • Press CTRL and drag & drop the entries to the new Address Book. Check the number of Address Cards, they have to be identical.
  • Go back to the Personal Address Bock, mark all messages and delete them.
  • Restart Thunderbird, open the Address Book menu again
  • Now click on the new Address Book and mark all messages. Drag & Drop them back to the Personal Address Book. Compare the figures again, make sure they are identical.
  • Restart Thunderbird once again and use the recreated Address Book

You can use a Thunderbird extension instead as well, if you prefer that. Check out our review of the Thunderbird Duplicate Contact Manager extension for instructions on how to use it instead.

Instead of having to create a new address book and copy data to it from the old, you can use the extension instead to do so.

To use it, open the address book after you have installed it and select find and manage duplicates from the Tools menu there.


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  1. Frank Cahill said on March 20, 2008 at 8:29 pm

    HI I am running TBird on Vista. It will not allow copy and past from within the Address Book!

    Is this a problem with Vista only?
    I have copied my addresses using LDIF format from an XP machine but I cannot get these addresses into the abook.mab file. They are currently sitting in impab-1.mab.



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