How can I delete all emails and empty my email inbox?
If you want to delete ALL of your emails in one go, you can simply delete your e-mail account from cPanel and recreate it, this will delete all of your emails. This will also delete any address books or contacts you may have saved under the email account, make sure you backup your address book.
If you wish to manually delete the emails, you can login to webmail at
www.yourdomain.com/webmailand use a webmail client of your choice to delete every single email.