Have you got multiple emails in your account that is of no use to you, and now you want to know as How to delete thousands of emails at the same time in yahoo? Here is the help for you. Open the Yahoo inbox, check option where you will get option to mark all unread mails, read mails etc. Once you will mark on open unread mails then mails that have not been opened by you will get selected automatically from your inbox page. Now click on delete button to delete mails in group. You can also call to support team to get assistance.