Yahoo! Mail is a popular Web-based e-mail service that lets you send and retrieve messages through a Web browser. Your Yahoo! Mail account is set up with a few standard folders, including a Trash folder that contains messages that you have deleted. If you decide that you do need a message that you have deleted, you can retrieve it from the Trash folder.
Open a browser and log in to your Yahoo! e-mail account.
Click on the small Trash icon in the left column. This will show the messages that you have deleted.
Drag the message that you want to retrieve onto the Inbox icon in the left column if your Yahoo! mail allows you do that. Some older versions do not let you drag messages. In this case, click on the message that is in your Trash folder, hit the "Move" button, scroll down and click "Inbox."