1. At the top of your dashboard, click the message icon to open the Inbox page.

  2. On the top right, click the Sent button to open the Outbox page. All sent messages will be displayed.

  3. Select the checkboxes for the message that you want to delete or select the checkbox in the header. All messages that are currently visible on the page will get selected.

                                                                   Fig 1.

  1. Click the Delete button.

For more information, watch this-