Thunderbird - Managing duplicate mails

October 2016


Sometimes, when you retrieve emails in your favorite mail client, the server may disconnects. In some cases you get 2 times (or more) the same messages and you are then obliged to remove them manually.


Fortunately, if you use Thunderbird, there is a solution to avoid such duplication upon reception.
  • Just go into Thunderbird options (Tools -> Options (Windows).
  • Click on the icon "Advanced" then click the button "Configuration Editor" under the "General" tab.
  • You will then have access to a list of options (just as with the about: config in Firefox).
  • Look for one that is called mail.server.default.dup_action (by typing in the filter). Right click on this key and change the value through the following figure:
  • - 0 if you want to load the duplicate mails as usual
  • - 1 if you want to delete automatically (and directly) emails duplicated once they have been approved.
  • - 2 if you want to duplicate the mail in the trash
  • - 3 if you want to mark the duplicate mails as "already read"

Related :

This document entitled « Thunderbird - Managing duplicate mails » from CCM ( is made available under the Creative Commons license. You can copy, modify copies of this page, under the conditions stipulated by the license, as this note appears clearly.