Removing duplicate emails in Thunderbird

Question

I need to stop the duplicate mail (which is already in my mail box) in Thunderbird or any mail box.

Are there any filters for this?

Answer 1

There is no need for an extension.

There's a config option in Thunderbird to deal with duplicate messages. You can delete, move to trash or mark as read if you don't want them appearing in your inbox like normal mail (who would? - I don't know why this isn't set to trash by default).

Ghacks has an article about the topic: Automatically remove duplicate mails in Thunderbird.

Access the config editor via the “Advanced Options” tab (Tools → Options → Advanced → Config Editor) and modify the mail.server.default.dup_action flag:

• keep = 0
• delete = 1
• move to trash = 2
• mark as read = 3

It is recommended to experiment with "move to trash" and "mark as read" settings before using the delete option.

Answer 2

How about the "Remove Duplicate Messages" plugin for Thunderbird?

Answer 3

I believe there's more development effort behind the "Alternate" version of the "Remove Duplicate Messages" add-on. (Last update March 11, 2011 as of this writing). This is the one I use.

https://addons.mozilla.org/en-US/thunderbird/addon/remove-duplicate-messages-alte/

Note that it refuses to work on "special" folders by default, and you have to enable this option in the settings: → "Message Comparison" tab → UNcheck "Skip Special Folders (Sent, Drafts etc.)."

I've used this extension on several thousand messages at once (merging mail archives from different mail clients that had used POP to fetch mail) and it hasn't burned me yet. You probably won't want to try it on one of Thunderbird 3's new "unified" folders, as I'm not sure that will turn out too well. Rather, switch to the "All Folders" view and select two individual folders using the context menu option Set original message folder(s) for next duplicate search.

And make backups.

Answer 4

Try reading this

It has a couple of suggestions for extensions to delete duplicates and also has some tips on avoiding them in the first place.

Answer 5

Remove Duplicate Messages (Alternate for Thunderbird 68-next version:

Answer 6

Or try some add-Ons:

Like this, https://addons.mozilla.org/en-US/thunderbird/addon/remove-duplicate-messages/

or read this: http://email.about.com/od/mozillathunderbird/gr/remove_duplicat.htm

Answer 7

Before doing anything else, I rather strongly recommend making a backup of all your emails in Thunderbird.
Make sure Thunderbird is closed. Then do for example as follows from a cmd.exe command line:

chDir /D C:\Users\%UserName%\
"%ProgramFiles%\7-Zip\7z.exe" a Thunderbird.zip AppData\Roaming\Thunderbird\

Your backup will now be the zip file C:\Users\%UserName%\Thunderbird.zip.

Below I will explain:

1. how to prevent future duplicates in incoming messages, and
2. how to remove already existing duplicates from Thunderbird.

Here we go.

1. In Thunderbird click Tools > Options and then Advanced > Config Editor....
   You'll have to promise to be careful.
   In the search box paste mail.server.default.dup_action. Set Value to 2. (The default is 0.)
   Close the about:config window. From now on you should expect not to receive any new duplicates.
   Any duplicates downloaded should end up in Trash.

2. But any duplicate emails you already have in Thunderbird are still there. Here is how to fix this.
   In Thunderbird click Help > About Thunderbird to see what version of Thunderbird you are using.
   Close Thunderbird, go to https://addons.thunderbird.net/en-US/thunderbird/addon/removedupes/versions/ and download the version of the Remove Duplicate Messages add-on that is compatible with your version.
   To install it, select Tools > Add-ons. At the top of the page, click the gearwheel, select Install Add-on From File... and locate the downloaded add-on. In the upper right corner click Restart Now.

In the Add-ons Manager choose Extensions and then Options for the add-on.
Uncheck Skip special folders (Sent, Drafts etc.) and click OK.
Now select Tools > Remove Duplicates. Up in the right corner, under In every set of dupes, keep: click First copy. (Or whichever you prefer - it shouldn't matter since they are duplicates, right?) Click OK.
If you have (had) any duplicates, expect to see Moving xxx messages of yyy to Trash down in the left corner of Thunderbird.

References:
https://www.7-zip.org/
https://www.ghacks.net/2007/05/18/automatically-remove-duplicate-mails-in-thunderbird/
http://kb.mozillazine.org/Duplicate_messages_received

Answer 8

The kind of de-duping that you're asking for is usually configured on the server. For example, one can configure Microsoft Exchange to recognize that a particular user is also on a distribution list, and only send one copy:

http://technet.microsoft.com/en-us/library/dd577073%28EXCHG.80%29.aspx

On the client side, your only real option is to create a filter. Differentiating the two emails is not immediately obvious to me. Here's what I would do:

1. In firefox, double click both emails to open them in separate tabs
2. For each email, choose View->Headers->All
3. Compare the headers in both and see if you can determine a differentiating factor
4. If you succeed in (3), then create a custom filter and delete the message based upon the header.