It happens sometimes that you find duplicate mails in your inbox in Thunderbird. This could happen for instance when you pull new emails from the mail server and get disconnected during that process. It could happen then that those emails will be retrieved again when you check for mails. Thunderbird has a nice hidden variable that defines how it should treat duplicate mails and I’m going to tell you how to set it correctly so that duplicate mails are removed automatically.
You have to click on Tools > Options to open the options in Thunderbird. Click on the Advanced tab there and select Config Editor under Advanced Configuration. This looks similar to the about:config shortcut in Firefox then. Enter mail.server.default.dup_action in the filter and the entry should be shown alone in the main window. Now right-click that entry and select modify from the menu. You can change the parameter to the following values:
- 0 – this is the default value. It retrieves duplicate mails like normal mails.
- 1 – if you set the value to 1 duplicate mails will be deleted automatically once retrieved
- 2 – if you set the value to 2 duplicated mails will be moved right into the trash
- 3 – the value 3 finally marks duplicate mails as read
If you want to delete duplicate mails automatically in Thunderbird you select the value 1.
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Thanks for knowing me about config editor.It is helping me a lot.
This problem only seems to happen in Windows Vista. An old XP machine does not do this. I have dual boot Vista and Linux and it is endemic on Vista, but I have never had it on Linux [Suse 11.1].
We have to leave our mail on the server, so we can pick it up in different locations, so the Mozilla idea of removing mail from the server is not helpful. However, the layout of Thunderbird in Linux and WIndows is different and this make much advice hard to follow. For example TOOLS in Linux has fewer options and ACCOUNTS are under EDIT not TOOLS.
If only the Mozilla teams would get together and make the Linux and Windows versions as nearly the same as possible, it would make life easier..
Just a word of warning for unsuspecting ‘fiddlers’, if you change this value in the config editor you are very brave.
Has the author of this article stopped to consider which parametres the config editor uses to determine if emails are the same?
Changing this value to 1 certainly will stop duplicate emails, and most others as well.
Lucky I discovered this before I lost too many orders!
Does’t matter if its a different order – it just deletes all orders because there are already ‘orders’ in the inbox!
The search for the elusive cause of duplicates continues, until then I’ll just stick to the duplicate removal tool which I set to: Author, Message ID, Send time & Subject.
Well I made the suggested change, but it changed nothing. The same duplications occur every time I open Thunderbird. I know this is a Thunderbird problem because I don’t get duplications for that email address on my phone. It only seems to happen for the current month. No past emails are duplicated. Something is going on with the last version or two of Thunderbird and I think they should make this a priority. It’s too annoying and makes me not want to ever check my mail thru Thunderbird. If it keeps happening I will abandon Thunderbird. There are scores of posts on this. If they don’t care, I don’t care.