Remember that the Incoming type should be chosen as IMAP while adding the account.

Go ahead and add your Gmail or other webmail address in Thunderbird. Delete duplicate emails by Mozilla Thunderbird Earlier we had shared the way to delete duplicate emails in Outlook and now here is the way to remove duplicate emails in Thunderbird. Outlook comes with Microsoft Office suite which is a paid package but if you want to have a free and reliable desktop mailing client, I would recommend Mozilla Thunderbird. That’s why I would suggest you to use desktop email client like Microsoft Outlook or Mozilla Thunderbird. As Gmail is not having any standard option to delete or clean duplicate emails in Inbox. Same is the case with other webmail services as well. For example, Gmail provides ~7GB of space to free accounts and if you want to have more space, you need to pay $50 per year to take Google Apps premium service. Are you having lot many duplicate emails in your webmail service like Gmail, AOL, Hotmail or custom domain webmail? As these services give your limited amount of memory storage for free and charge for extra space, that’s why it is recommended to keep cleaning your Inbox.

Delete duplicates in outlook 2011