Removing Duplicate Messages

How to remove duplicate messages using Thunderbird

If a user has duplicate messages they can easily be cleaned up with the following Thunderbird extension:

If you have duplicate messages (e.g. from merging folders or downloading messages several times) you can use this tool to find and remove them from the selected folder and its subfolder by right clicking on a folder and choosing "Remove Duplicate Messages". It allows you to configure what you want to compare (sender, messageid, subject, ...)

Thunderbird Remove Duplicate Messages Extension

  • Install the plugin and connect to the mailbox which has duplicate messages using Thunderbird via IMAP.
  • Click all folders one time to retrieve the headers.
  • Right click the top level (above the inbox) and start the Remove Duplicates Plugin.
  1. has a linear algorithm, which means he removed duplicates out of my roughly 50.000 emails within one minute.
  2. can also compare mail bodies for advanced duplicates detection.