The way to eliminate duplicate e-mails in an inbox varies depending on your e-mail provider. A standard approach could be through using the search feature of each inbox, but most providers have their own features to expedite this process. Alternately, you can download a program that finds and deletes all duplicate e-mails from a given program automatically. For example, for Microsoft Outlook, a free trial version of Duplicate Email Remover is available as an add-in.
Log in to your e-mail client. Find the search field. You usually can find them along the top. In Gmail, it is just below the upper border of the Web page to the left. In Windows Live Mail, it is at the top-right of the inbox field just above the words "Arrange by." In Yahoo! it is in a similar location as in Gmail.
Type the subject of the duplicate e-mail and press "Enter." Many results are likely to appear, but almost all e-mail clients give the option to refine your search once you receive your results. In Yahoo!, search refinement options appear in the grid on the left. In Windows Live Mail and Gmail, it will be along the top. Narrow down your search until only the duplicate e-mails appear.
Click "Select all." Though Yahoo! Mail and Windows Live Mail offer this option, Gmail expedites this by asking what you would like to do with your search results. Once all of the duplicate e-mails are selected in Yahoo! Mail and Windows Live Mail, click "Move to" and then select "Trash." In both Yahoo! and Windows Live Mail, this option appears at the top. In Gmail, you have the option to delete or archive your duplicate e-mails. Archiving it will eliminate it from your inbox, but will prevent permanent deletion.
Click on the cog graphic that appears next to "Folders" along the right when you hover your cursor over it.
Select "Create new folder." Name the folder after the sender of the duplicate e-mails.
Select an e-mail from the sender of the duplicate e-mails.
Click on "Sweep" that appears along the top and then select "Move all from ..."
Select the new folder from the right to open it. Once within the folder, perform a search for the subject of the duplicate e-mails. Once they appear, choose "Select all" from the top and then "Move to ..." to send them to the trash.
Click on "Mail search" that appears next to the search field in your inbox to open the advanced search options.
Enter all known information about your duplicate e-mail in the corresponding fields.
Check the uppermost box for selecting e-mails to select all search results and then click the "Delete" button.
Select one of the duplicate e-mails.
Click "More actions ..." along the top to open the menu and select "Filter messages like these."
Enter in all known information about the duplicate e-mails and then click "Next Step" that appears below the information fields.
Select which option--whether archiving or deleting--that you prefer to apply to the duplicate e-mails.
Ensure that you preserve at least one copy of your duplicate e-mails if desired, since e-mails deleted from the trash likely cannot be recovered. Instead of searching for duplicate subjects, you can also find duplicate e-mails with differing subject lines by replacing all instances of "subject" in the previous standard instructions with any other aspect that each duplicate e-mail shares--such as the first line of the message.