About this Add-on
This add-on lets you search messages in one or several folders to locate duplicates: Messages which are identical - according to some comparison criteria you chose.
- Wide choice of comparison criteria (subject, author, send time, CC list, flags, etc).
- Review dialog for double-checking which duplicates to delete and which to keep.
- Relatively fast; should easily be able to handle 100K emails and more
- Supports comparison of message bodies as a comparison criteria (but this slows thing down of course).
- Good performance on local folders with large number of messages; reasonable performance with IMAP and RSS accounts.
- Spiffy toolbar button+menu for quick access.
- Free (GPL/LGPL/MPL license)
There's also a SeaMonkey version, though not as frequently tested.
I had tried contacting the author of the original 'Remove Duplicate Messages' several times, without success. I would have liked to join forces and have just one extension, but that doesn't seem to work out.
Also, some locales are incomplete - help with them would be appreciated. Visit the BabelZilla translation website.
* Dropped the "(Alternate)" suffix from the name. From now on this extension will be known as "Remove Duplicate Messages".
* Logic change: Missing values are now assumed to have (unknown) unique values, so they are not considered to be duplicates of other missing values in the same field ; a (hidden) preference controls this behavior.
* **Compatibility**: Compatible with Thunderbird 68, 78 and probably all beta versions in-between.
* **Compatibility**: No longer compatible with Seamonkey 1.x, Toolkitized Seamonkey (2.x)
* **Compatibility**: No longer compatible with Thunderbird 30...67.
* **Fix**: Status flag comparison criteria was present only on the menubutton but not in the preferences dialog - now it appears in both.
Internal changes (no user visibility):
* No longer using JARs
* Reworked the directory structure
* Dropped some files only in use by previous TB versions (but not all files for now)
* Using John Bieling's "WindowListener" from [here](https://github.com/thundernest/addon-developer-support/), as an extension loader; see [this guide](https://github.com/thundernest/addon-developer-support/wiki/Using-the-WindowListener-API-to-convert-a-Legacy-Overlay-WebExtension-into-a-MailExtension-for-Thunderbird-78) regarding how to use it.
* Now using service getters provided by `Services.jsm` and `MailServices.jsm` whenever possible.
* Now logging using a plain and simple `console.log()`/`console.error()`.
* **Fix:** Corrected the default value of the hidden preference for allowing MD5 substitutes for Message ID (no effect on behavior).
- Source code released under Mozilla Public License Version 1.1