Mass delete of duplicate emails

[RobEW]

Hello. New to this forum but I've had a search for this topic and found nothing relevant, so hope you won't mind a newbie question.

This morning my Thunderbird client (running on Windows 7, set up as POP3) decided for some reason (possibly a change at my email host - Virgin media * ) to download some thousands of historic emails again. Now I have everything ( or almost everything) twice on my computer, with the newly downloaded versions marked as unread.

Whatever glitch caused this seems not to be recurring as I've rebooted, restarted thunderbird and not had it try to download everything again.

However it would be nice for me to find some quick way to delete the (several thousand) duplicates without losing the originals. Does anyone know a suitable method? Some are in my inbox; others in various other folders, automatically moved on the basis of the rules I supplied.

Thanks in anticipation.

Rob

= = =

Here's part of an email from Virgin Media which makes me think they may have caused the extra download:

Hello,

It's here! Welcome to your new Virgin Media Mail.

If you're using our webmail service, you'll have seen our new simple layout. Sending, receiving and managing your emails is a doddle. But if you need to, you can get up to speed on the changes by selecting a guided tour from the Virgin Media Mail settings menu in webmail or by visiting virginmedia.com/emailswitch

If you use an email client (like Outlook or Thunderbird), things won't look very different, so you can carry on using email, just the way you like to.

Please be aware, if you use POP3 to download emails to your email client, it's really important that your client leaves a copy of the message on the server, so you can see it on another device (like your phone or tablet) or through webmail. Please check your settings as soon as you can.

[DanRaisch]

This extension might be helpful to you -- https://addons.mozilla.org/en-US/thunde ... ages-alte/

[RobEW]

Thanks - I'll give it a go.

[RobEW]

I had a go. Nothing on computers is ever as simple as it seems is it?

It downloaded something with an xpi extension which my computer didn't recognise.

Research using Google suggested I needed Firefox installed.

I downloaded, installed and tested FireFox.

Open the xpi file again and select Firefox and I get a message asking if I want firefox to be my default browser, which I decline. Then it gives me a blank screen.

I try again, this time accepting that FireFox can be my default browser. Now I get a message saying "This add-on could not be installed because it has not been verified" and a "Learn more link".

The "Learn more" text seems to be suggesting that I need to download any addons from a site which is authorised ...

Sigh ...

Thanks for your suggestion anyway.

[DanRaisch]

To install a Thunderbird extension do the following:
Right click the download link on the extension's home page and choose "Save Link As...". Then, in Thunderbird, go to Tools->Addons->Extensions tab->click on the "Gear" icon and select "Install Add-on from File" from the drop down list. Navigate to the just downloaded .xpi file and select it. Click on the "Open" button. The installation will now begin. You will need to close and reopen Thunderbird to complete the install.