thunderbird duplicate email delete function

first of all, why do you get every email twice?  are they different accounts delivered to same place (alias forwarding)?
from the client side it seems to me that war1's idea is the best available.  however without knowing why you get every email twice its hard to advice how to stop it.

What version of Thunderbird do you have?  If it is an older version (>= 1.5) you could download Delete Duplicate Messages extension found here: https://addons.mozilla.org/en-US/thunderbird/addon/956.  This has worked wonders for me in the past but unfortunately it is not compatible with Thunderbird 2.0 and higher.

Hiroyuki,

Your question is to how to delete the duplicate emails, not on how were they created. There are a few things you can check to stop duplicate email messages.

Start by checking Rules to be sure that copies are not being made to the Inbox, and make sure that all your rules end in "Stop Processing" actions.

Then check the task manager to be sure that there is only one instace of Outlook running. Two instances of outlook.exe running can produce two messages arriving at the same time. You will need to then determine why two instances of Outlook were running in the first place.

Another thing you can do is to delete/remove ALL your e-mail accounts and recreate them. This worked for some people.

Also, if your running Outlook XP, be sure that you are at service pack 2 or later. You can tell if you need to upgrade at Microsoft Product Updates.

Finally, another person had this happen when he had two e-mail accounts set up - using two e-mail addresses, but the same POP3 incoming and same SMTP outgoing. What happened is that the second account was getting the e-mails from the POP3 server before they were actually deleted after the first account was finished. If this is the problem you can disable the receive on the second account. There is a Microsoft article explaining the problem more thoroughly at http://support.microsoft.com/?kbid=284404.

http://www.sperrysoftware.com/Outlook/Outlook-Duplicates.asp#Q1

war1, I think you got confused on this one.  Thunderbird 2 is the client, not Outlook.  Also I requested the why of the matter.  Reason is that to me it sounded like no duplicates were wanted.  So instead of just trying to deal with the problem when it arises, stop it from happening in the first place.  Just assumed that's what the asker would want I guess.

hiroyuki,  this still shouldn't happen.  By choosing the leave on server option you can redownload those emails on a different client (whether different host or different software).  However they shouldn't be for the same client that downloaded them before.  The client should know it downloaded them and not request them again (or the server knows; not completely sure how that communication works yet).  The only time I have ever seen this happen is the when the client lost connection after downloading a bunch of email, but didn't confirm it download them.  Then the next check, it redownloaded a bunch of email it had just downloaded.

Sorry, Hirojuki and Cyclops.  I did post as if you were using Outlook.  Some of my last post still applies to Thunderbird.

Hirojuki,

Since you are using Thunderbird, does all your accounts in Thunderbird receive duplicate emails?

1. Start by checking Rules to be sure that copies are not being made to the Inbox, and make sure that all your rules end in dtop processing more rules.

2. Then check the task manager to be sure that there is only one instance of Thunderbird running. Two instances of outlook.exe running can produce two messages arriving at the same time. You will need to then determine why two instances of Outlook were running in the first place.

3. Another thing you can do is to delete/remove ALL your e-mail accounts and recreate them. This worked for some people.